Strings These functions all manipulate strings in various ways. Some more specialized sections can be found in the regular expression and URL handling sections. For information on how strings behave, especially with regard to usage of single quotes, double quotes, and escape sequences, see the Strings entry in the Types section of the manual. addcslashes Quote string with slashes in a C style string addcslashes string str string charlist Returns a string with backslashes before characters that are listed in charlist parameter. It escapes \n, \r etc. in C-like style, characters with ASCII code lower than 32 and higher than 126 are converted to octal representation. Be careful if you choose to escape characters 0, a, b, f, n, r, t and v. They will be converted to \0, \a, \b, \f, \n, \r, \t and \v. In PHP \0 (&null;), \r (carriage return), \n (newline) and \t (tab) are predefined escape sequences, while in C all of these are predefined escape sequences. charlist like "\0..\37", which would escape all characters with ASCII code between 0 and 31. $escaped = addcslashes($not_escaped, "\0..\37!@\177..\377"); When you define a sequence of characters in the charlist argument make sure that you know what characters come between the characters that you set as the start and end of the range. echo addcslashes('foo[]', 'A..z'); // All upper and lower-case letters will be escaped // ..but so will the [\]^_` and space characters. Also, if the first character in a range has a lower ASCII value than the second character in the range, no range will be constructed. Only the start, end and period characters will be escaped. Use the ord function to find the ASCII value for a character. echo addcslashes("zoo['.']", 'z..A'); /* output: \zoo['\.'] */ Added in PHP 4 See also stripcslashes, stripslashes, htmlspecialchars, and quotemeta. addslashes Quote string with slashes string addslashes string str Returns a string with backslashes before characters that need to be quoted in database queries etc. These characters are single quote ('), double quote ("), backslash (\) and NUL (the &null; byte). See also stripslashes, htmlspecialchars, and quotemeta. bin2hex Convert binary data into hexadecimal representation string bin2hex string str Returns an ASCII string containing the hexadecimal representation of str. The conversion is done byte-wise with the high-nibble first. chop Alias of rtrim This function is an alias of rtrim. chop is different than the Perl chop() function, which removes the last character in the string. chr Return a specific character string chr int ascii Returns a one-character string containing the character specified by ascii. $str .= chr(27); /* add an escape character at the end of $str */ /* Often this is more useful */ $str = sprintf("The string ends in escape: %c", 27); You can find an ASCII-table over here: &url.asciitable;. This function complements ord. See also sprintf with a format string of %c. chunk_split Split a string into smaller chunks string chunk_split string string int chunklen string end Can be used to split a string into smaller chunks which is useful for e.g. converting base64_encode output to match RFC 2045 semantics. It inserts every chunklen (defaults to 76) chars the string end (defaults to "\r\n"). It returns the new string leaving the original string untouched. # format $data using RFC 2045 semantics $new_string = chunk_split(base64_encode($data)); This function is significantly faster than ereg_replace. This function was added in 3.0.6. convert_cyr_string Convert from one Cyrillic character set to another string convert_cyr_string string str string from string to This function returns the given string converted from one Cyrillic character set to another. The from and to arguments are single characters that represent the source and target Cyrillic character sets. The supported types are: k - koi8-r w - windows-1251 i - iso8859-5 a - x-cp866 d - x-cp866 m - x-mac-cyrillic count_chars Return information about characters used in a string mixed count_chars string string mode Counts the number of occurrences of every byte-value (0..255) in string and returns it in various ways. The optional parameter Mode default to 0. Depending on mode count_chars returns one of the following: 0 - an array with the byte-value as key and the frequency of every byte as value. 1 - same as 0 but only byte-values with a frequency greater than zero are listed. 2 - same as 0 but only byte-values with a frequency equal to zero are listed. 3 - a string containing all used byte-values is returned. 4 - a string containing all not used byte-values is returned. This function was added in PHP 4.0. crc32 Calculates the crc32 polynomial of a string int crc32 string str Generates the cyclic redundancy checksum polynomial of 32-bit lengths of the str. This is usually used to validate the integrity of data being transmitted. See also: md5 crypt DES-encrypt a string string crypt string str string salt crypt will return an encrypted string using the standard Unix DES encryption method. Arguments are a string to be encrypted and an optional two-character salt string to base the encryption on. See the Unix man page for your crypt function for more information. If the salt argument is not provided, one will be randomly generated by PHP. Some operating systems support more than one type of encryption. In fact, sometimes the standard DES encryption is replaced by an MD5 based encryption algorithm. The encryption type is triggered by the salt argument. At install time, PHP determines the capabilities of the crypt function and will accept salts for other encryption types. If no salt is provided, PHP will auto-generate a standard 2-character DES salt by default, unless the default encryption type on the system is MD5, in which case a random MD5-compatible salt is generated. PHP sets a constant named CRYPT_SALT_LENGTH which tells you whether a regular 2-character salt applies to your system or the longer 12-char MD5 salt is applicable. If you are using the supplied salt, you should be aware that the salt is generated once. If you are calling this function recursively, this may impact both appearance and, to a certain extent, security. The standard DES encryption crypt contains the salt as the first two characters of the output. On systems where the crypt() function supports multiple encryption types, the following constants are set to 0 or 1 depending on whether the given type is available: CRYPT_STD_DES - Standard DES encryption with a 2-char SALT CRYPT_EXT_DES - Extended DES encryption with a 9-char SALT CRYPT_MD5 - MD5 encryption with a 12-char SALT starting with $1$ CRYPT_BLOWFISH - Extended DES encryption with a 16-char SALT starting with $2$ There is no decrypt function, since crypt uses a one-way algorithm. See also: md5. echo Output one or more strings echo string arg1 string argn... Outputs all parameters. echo is not actually a function (it is a language construct) so you are not required to use parentheses with it. In fact, if you want to pass more than one parameter to echo, you must not enclose the parameters within parentheses. <?php echo "Hello World"; echo "This spans multiple lines. The newlines will be output as well"; echo "This spans\nmultiple lines. The newlines will be\noutput as well."; echo "escaping characters is done \"Like this\"." //You can use variables inside of an echo statement $foo = "foobar"; $bar = "barbaz"; echo "foo is $foo"; // foo is foobar // Using single quotes will print the variable name, not the value echo 'foo is $foo'; // foo is $foo // If you are not using any other characters, you can just echo variables echo $foo; // foobar echo $foo,$bar; // foobarbarbaz // because echo is not a function, following code is invalid. ($some_var) ? echo('true'): echo('false'); // However, the following examples will work: ($some_var) ? print('true'): print('false'); // print is a function echo $some_var ? 'true': 'false'; // changing the statement around ?> echo also has a shortcut syntax, where you can immediately follow the opening tag with an equals sign. I have <?=$foo?> foo. See also: print, printf, and flush. explode Split a string by string array explode string separator string string int limit Returns an array of strings, each of which is a substring of string formed by splitting it on boundaries formed by the string separator. If limit is set, the returned array will contain a maximum of limit elements with the last element containing the whole rest of string. If an empty string ("") is used as the separator argument, then explode will return &false;. If separator contains a value that is not contained in the string argument, thenexplode will return the string argument. The limit parameter was added in PHP 4.0.1 $pizza = "piece1 piece2 piece3 piece4 piece5 piece6"; $pieces = explode(" ", $pizza); Although implode can for historical reasons accept its parameters in either order, explode cannot. You must ensure that the separator argument comes before the string argument. See also preg_split, spliti, split and implode. get_html_translation_table Returns the translation table used by htmlspecialchars and htmlentities string get_html_translation_table int table int quote_style get_html_translation_table will return the translation table that is used internally for htmlspecialchars and htmlentities. There are two new defines (HTML_ENTITIES, HTML_SPECIALCHARS) that allow you to specify the table you want. And as in the htmlspecialchars and htmlentities functions you can optionally specify the quote_style you are working with. The default is ENT_COMPAT mode. See the description of these modes in htmlspecialchars. $trans = get_html_translation_table(HTML_ENTITIES); $str = "Hallo & <Frau> & Krämer"; $encoded = strtr($str, $trans); The $encoded variable will now contain: "Hallo &amp; &lt;Frau&gt; &amp; Kr&auml;mer". The cool thing is using array_flip to change the direction of the translation. $trans = array_flip($trans); $original = strtr($str, $trans); The content of $original would be: "Hallo & <Frau> & Krämer". This function was added in PHP 4.0. See also: htmlspecialchars, htmlentities, strtr, and array_flip. get_meta_tags Extracts all meta tag content attributes from a file and returns an array array get_meta_tags string filename int use_include_path Opens filename and parses it line by line for <meta> tags of the form <meta name="author" content="name"> <meta name="tags" content="php3 documentation"> </head> <!-- parsing stops here --> (pay attention to line endings - PHP uses a native function to parse the input, so a Mac file won't work on Unix). The value of the name property becomes the key, the value of the content property becomes the value of the returned array, so you can easily use standard array functions to traverse it or access single values. Special characters in the value of the name property are substituted with '_', the rest is converted to lower case. Setting use_include_path to 1 will result in PHP trying to open the file along the standard include path. hebrev Convert logical Hebrew text to visual text string hebrev string hebrew_text int max_chars_per_line The optional parameter max_chars_per_line indicates maximum number of characters per line will be output. The function tries to avoid breaking words. See also hebrevc hebrevc Convert logical Hebrew text to visual text with newline conversion string hebrevc string hebrew_text int max_chars_per_line This function is similar to hebrev with the difference that it converts newlines (\n) to "<br>\n". The optional parameter max_chars_per_line indicates maximum number of characters per line will be output. The function tries to avoid breaking words. See also hebrev htmlentities Convert all applicable characters to HTML entities string htmlentities string string int quote_style This function is identical to htmlspecialchars in all ways, except that all characters which have HTML character entity equivalents are translated into these entities. Like htmlspecialchars, it takes an optional second argument which indicates what should be done with single and double quotes. ENT_COMPAT (the default) will only convert double-quotes and leave single-quotes alone. ENT_QUOTES will convert both double and single quotes, and ENT_NOQUOTES will leave both double and single quotes unconverted. At present, the ISO-8859-1 character set is used. Note that the optional second argument was added in PHP 3.0.17 and PHP 4.0.3. See also htmlspecialchars and nl2br. htmlspecialchars Convert special characters to HTML entities string htmlspecialchars string string int quote_style Certain characters have special significance in HTML, and should be represented by HTML entities if they are to preserve their meanings. This function returns a string with some of these conversions made; the translations made are those most useful for everyday web programming. If you require all HTML character entities to be translated, use htmlentities instead. This function is useful in preventing user-supplied text from containing HTML markup, such as in a message board or guest book application. The optional second argument, quote_style, tells the function what to do with single and double quote characters. The default mode, ENT_COMPAT, is the backwards compatible mode which only translates the double-quote character and leaves the single-quote untranslated. If ENT_QUOTES is set, both single and double quotes are translated and if ENT_NOQUOTES is set neither single nor double quotes are translated. The translations performed are: '&' (ampersand) becomes '&amp;' '"' (double quote) becomes '&quot;' when ENT_NOQUOTES is not set. ''' (single quote) becomes '&#039;' only when ENT_QUOTES is set. '<' (less than) becomes '&lt;' '>' (greater than) becomes '&gt;' $new = htmlspecialchars("<a href='test'>Test</a>", ENT_QUOTES); Note that this function does not translate anything beyond what is listed above. For full entity translation, see htmlentities. Also note that the optional second argument was added in PHP 3.0.17 and PHP 4.0.3. See also htmlentities and nl2br. implode Join array elements with a string string implode string glue array pieces Returns a string containing a string representation of all the array elements in the same order, with the glue string between each element. $colon_separated = implode(":", $array); implode can, for historical reasons, accept its parameters in either order. For consistency with explode, however, it may be less confusing to use the documented order of arguments. See also explode, join, and split. join Join array elements with a string string join string glue array pieces join is an alias to implode, and is identical in every way. See also explode, implode, and split. levenshtein Calculate Levenshtein distance between two strings int levenshtein string str1 string str2 int levenshtein string str1 string str2 int cost_ins int cost_rep int cost_del int levenshtein string str1 string str2 function cost This function returns the Levenshtein-Distance between the two argument strings or -1, if one of the argument strings is longer than the limit of 255 characters (255 should be more than enough for name or dictionary comparison, and nobody serious would be doing genetic analysis with PHP). The Levenshtein distance is defined as the minimal number of characters you have to replace, insert or delete to transform str1 into str2. The complexity of the algorithm is O(m*n), where n and m are the length of str1 and str2 (rather good when compared to similar_text, which is O(max(n,m)**3), but still expensive). In its simplest form the function will take only the two strings as parameter and will calculate just the number of insert, replace and delete operations needed to transform str1 into str2. A second variant will take three additional parameters that define the cost of insert, replace and delete operations. This is more general and adaptive than variant one, but not as efficient. The third variant (which is not implemented yet) will be the most general and adaptive, but also the slowest alternative. It will call a user-supplied function that will determine the cost for every possible operation. The user-supplied function will be called with the following arguments: operation to apply: 'I', 'R' or 'D' actual character in string 1 actual character in string 2 position in string 1 position in string 2 remaining characters in string 1 remaining characters in string 2 The user-supplied function has to return a positive integer describing the cost for this particular operation, but it may decide to use only some of the supplied arguments. The user-supplied function approach offers the possibility to take into account the relevance of and/or difference between certain symbols (characters) or even the context those symbols appear in to determine the cost of insert, replace and delete operations, but at the cost of losing all optimizations done regarding cpu register utilization and cache misses that have been worked into the other two variants. See also soundex, similar_text and metaphone. localeconv Get numeric formatting information array localeconv Returns an associative array containing localized numeric and monetary formatting information. localeconv returns data based upon the current locale as set by setlocale. The associative array that is returned contains the following fields: Array element Description decimal_point Decimal point character thousands_sep Thousands separator grouping Array containing numeric groupings int_curr_symbol International currency symbol (i.e. USD) currency_symbol Local currency symbol (i.e. $) mon_decimal_point Monetary decimal point character mon_thousands_sep Monetary thousands separator mon_grouping Array containing monetary groupings positive_sign Sign for positive values negative_sign Sign for negative values int_frac_digits International fractional digits frac_digits Local fractional digits p_cs_precedes &true; if currency_symbol precedes a positive value, &false; if it succeeds one p_sep_by_space &true; if a space separates currency_symbol from a positive value, &false; otherwise n_cs_precedes &true; if currency_symbol precedes a negative value, &false; if it succeeds one n_sep_by_space &true; if a space separates currency_symbol from a negative value, &false; otherwise p_sign_posn 0 Parentheses surround the quantity and currency_symbol 1 The sign string precedes the quantity and currency_symbol 2 The sign string succeeds the quantity and currency_symbol 3 The sign string immediately precedes the currency_symbol 4 The sign string immediately succeeds the currency_symbol n_sign_posn 0 Parentheses surround the quantity and currency_symbol 1 The sign string precedes the quantity and currency_symbol 2 The sign string succeeds the quantity and currency_symbol 3 The sign string immediately precedes the currency_symbol 4 The sign string immediately succeeds the currency_symbol The grouping fields contain arrays that define the way numbers should be grouped. For example, the grouping field for the en_US locale, would contain a 2 item array with the values 3 and 3. The higher the index in the array, the farther left the grouping is. If an array element is equal to CHAR_MAX, no further grouping is done. If an array element is equal to 0, the previous element should be used. setlocale(LC_ALL, "en_US"); $locale_info = localeconv(); echo "<PRE>\n"; echo "--------------------------------------------\n"; echo " Monetary information for current locale: \n"; echo "--------------------------------------------\n\n"; echo "int_curr_symbol: {$locale_info["int_curr_symbol"]}\n"; echo "currency_symbol: {$locale_info["currency_symbol"]}\n"; echo "mon_decimal_point: {$locale_info["mon_decimal_point"]}\n"; echo "mon_thousands_sep: {$locale_info["mon_thousands_sep"]}\n"; echo "positive_sign: {$locale_info["positive_sign"]}\n"; echo "negative_sign: {$locale_info["negative_sign"]}\n"; echo "int_frac_digits: {$locale_info["int_frac_digits"]}\n"; echo "frac_digits: {$locale_info["frac_digits"]}\n"; echo "p_cs_precedes: {$locale_info["p_cs_precedes"]}\n"; echo "p_sep_by_space: {$locale_info["p_sep_by_space"]}\n"; echo "n_cs_precedes: {$locale_info["n_cs_precedes"]}\n"; echo "n_sep_by_space: {$locale_info["n_sep_by_space"]}\n"; echo "p_sign_posn: {$locale_info["p_sign_posn"]}\n"; echo "n_sign_posn: {$locale_info["n_sign_posn"]}\n"; echo "</PRE>\n"; The constant CHAR_MAX is also defined for the use mentioned above. Added in PHP 4.0.5 See also: setlocale. ltrim Strip whitespace from the beginning of a string string ltrim string str string charlist This function returns a string with whitespace stripped from the beginning of str. Without the second parameter, ltrim will strip these characters: " " (ASCII 32 (0x20)), an ordinary space. "\t" (ASCII 9 (0x09)), a tab. "\n" (ASCII 13 (0x0D)), a newline. "\r" (ASCII 10 (0x0A)), a return. "\0" (ASCII 0 (0x00)), the NUL-byte. "\x0B" (ASCII 11 (0x0B)), a . You can also specify the characters you want to strip, by means of the charlist parameter. Simply list all characters that you want to be stripped. With .. you can specify a range of characters. ]]> The second parameter was added in PHP 4.0.7 See also trim and rtrim. md5 Calculate the md5 hash of a string string md5 string str Calculates the MD5 hash of str using the RSA Data Security, Inc. MD5 Message-Digest Algorithm, and returns that hash. See also: crc32 metaphone Calculate the metaphone key of a string string metaphone string str Calculates the metaphone key of str. Similar to soundex metaphone creates the same key for similar sounding words. It's more accurate than soundex as it knows the basic rules of English pronunciation. The metaphone generated keys are of variable length. Metaphone was developed by Lawrence Philips <lphilips@verity.com>. It is described in ["Practical Algorithms for Programmers", Binstock & Rex, Addison Wesley, 1995]. This function was added in PHP 4.0. nl2br Inserts HTML line breaks before all newlines in a string string nl2br string string Returns string with '<br />' inserted before all newlines. Starting with PHP 4.0.5, nl2br is now XHTML compliant. All versions before 4.0.5 will return string with '<br>' inserted before newlines instead of '<br />'. See also htmlspecialchars, htmlentities and wordwrap. ord Return ASCII value of character int ord string string Returns the ASCII value of the first character of string. This function complements chr. if (ord($str) == 10) { echo "The first character of \$str is a line feed.\n"; } You can find an ASCII-table over here: &url.asciitable;. See also chr. parse_str Parses the string into variables void parse_str string str array arr Parses str as if it were the query string passed via an URL and sets variables in the current scope. If the second parameter arr is present, variables are stored in this variable as an array elements instead. $str = "first=value&second[]=this+works&second[]=another"; parse_str($str); echo $first; /* prints "value" */ echo $second[0]; /* prints "this works" */ echo $second[1]; /* prints "another" */ print Output a string print string arg Outputs arg. See also: echo, printf, and flush. printf Output a formatted string int printf string format mixed args... Produces output according to format, which is described in the documentation for sprintf. See also: print, sprintf, sscanf, fscanf, and flush. quoted_printable_decode Convert a quoted-printable string to an 8 bit string string quoted_printable_decode string str This function returns an 8-bit binary string corresponding to the decoded quoted printable string. This function is similar to imap_qprint, except this one does not require the IMAP module to work. quotemeta Quote meta characters string quotemeta string str Returns a version of str with a backslash character (\) before every character that is among these: . \\ + * ? [ ^ ] ( $ ) See also addslashes, htmlentities, htmlspecialchars, nl2br, and stripslashes. rtrim Strip whitespace from the end of a string string rtrim string str string charlist This function returns a string with whitespace stripped from the end of str. Without the second parameter, rtrim will strip these characters: " " (ASCII 32 (0x20)), an ordinary space. "\t" (ASCII 9 (0x09)), a tab. "\n" (ASCII 13 (0x0D)), a newline. "\r" (ASCII 10 (0x0A)), a return. "\0" (ASCII 0 (0x00)), the NUL-byte. "\x0B" (ASCII 11 (0x0B)), a . You can also specify the characters you want to strip, by means of the charlist parameter. Simply list all characters that you want to be stripped. With .. you can specify a range of characters. ]]> The second parameter was added in PHP 4.0.7 See also trim and ltrim. sscanf Parses input from a string according to a format mixed sscanf string str string format string var1... The function sscanf is the input analog of printf. sscanf reads from the string str and interprets it according to the specified format. If only two parameters were passed to this function, the values parsed will be returned as an array. // getting the serial number $serial = sscanf("SN/2350001","SN/%d"); // and the date of manufacturing $mandate = "January 01 2000"; list($month, $day, $year) = sscanf($mandate,"%s %d %d"); echo "Item $serial was manufactured on: $year-".substr($month,0,3)."-$day\n"; If optional parameters are passed, the function will return the number of assigned values. The optional parameters must be passed by reference. // get author info and generate DocBook entry $auth = "24\tLewis Carroll"; $n = sscanf($auth,"%d\t%s %s", &$id, &$first, &$last); echo "<author id='$id'> <firstname>$first</firstname> <surname>$last</surname> </author>\n"; See also: fscanf, printf, and sprintf. setlocale Set locale information string setlocale mixed category string locale Category is a named constant (or string) specifying the category of the functions affected by the locale setting: LC_ALL for all of the below LC_COLLATE for string comparison, see strcoll LC_CTYPE for character classification and conversion, for example strtoupper LC_MONETARY for localeconv LC_NUMERIC for decimal separator (See also: localeconv) LC_TIME for date and time formatting with strftime If locale is the empty string "", the locale names will be set from the values of environment variables with the same names as the above categories, or from "LANG". If locale is zero or "0", the locale setting is not affected, only the current setting is returned. Setlocale returns the new current locale, or &false; if the locale functionality is not implemented in the platform, the specified locale does not exist or the category name is invalid. An invalid category name also causes a warning message. similar_text Calculate the similarity between two strings int similar_text string first string second double percent This calculates the similarity between two strings as described in Oliver [1993]. Note that this implementation does not use a stack as in Oliver's pseudo code, but recursive calls which may or may not speed up the whole process. Note also that the complexity of this algorithm is O(N**3) where N is the length of the longest string. By passing a reference as third argument, similar_text will calculate the similarity in percent for you. It returns the number of matching chars in both strings. soundex Calculate the soundex key of a string string soundex string str Calculates the soundex key of str. Soundex keys have the property that words pronounced similarly produce the same soundex key, and can thus be used to simplify searches in databases where you know the pronunciation but not the spelling. This soundex function returns a string 4 characters long, starting with a letter. This particular soundex function is one described by Donald Knuth in "The Art Of Computer Programming, vol. 3: Sorting And Searching", Addison-Wesley (1973), pp. 391-392. soundex("Euler") == soundex("Ellery") == 'E460'; soundex("Gauss") == soundex("Ghosh") == 'G200'; soundex("Hilbert") == soundex("Heilbronn") == 'H416'; soundex("Knuth") == soundex("Kant") == 'K530'; soundex("Lloyd") == soundex("Ladd") == 'L300'; soundex("Lukasiewicz") == soundex("Lissajous") == 'L222'; sprintf Return a formatted string string sprintf string format mixed args... Returns a string produced according to the formatting string format. The format string is composed of zero or more directives: ordinary characters (excluding %) that are copied directly to the result, and conversion specifications, each of which results in fetching its own parameter. This applies to both sprintf and printf. Each conversion specification consists of a percent sign (%), followed by one or more of these elements, in order: An optional padding specifier that says what character will be used for padding the results to the right string size. This may be a space character or a 0 (zero character). The default is to pad with spaces. An alternate padding character can be specified by prefixing it with a single quote ('). See the examples below. An optional alignment specifier that says if the result should be left-justified or right-justified. The default is right-justified; a - character here will make it left-justified. An optional number, a width specifier that says how many characters (minimum) this conversion should result in. An optional precision specifier that says how many decimal digits should be displayed for floating-point numbers. This option has no effect for other types than double. (Another function useful for formatting numbers is number_format.) A type specifier that says what type the argument data should be treated as. Possible types: % - a literal percent character. No argument is required. b - the argument is treated as an integer, and presented as a binary number. c - the argument is treated as an integer, and presented as the character with that ASCII value. d - the argument is treated as an integer, and presented as a (signed) decimal number. u - the argument is treated as an integer, and presented as an unsigned decimal number. f - the argument is treated as a double, and presented as a floating-point number. o - the argument is treated as an integer, and presented as an octal number. s - the argument is treated as and presented as a string. x - the argument is treated as an integer and presented as a hexadecimal number (with lowercase letters). X - the argument is treated as an integer and presented as a hexadecimal number (with uppercase letters). As of PHP version 4.0.6 the format string supports argument numbering/swapping. Here is an example: $format = "There are %d monkeys in the %s"; printf($format,$num,$location); This might output, "There are 5 monkeys in the tree". But imagine we are creating a format string in a separate file, commonly because we would like to internationalize it and we rewrite it as: $format = "The %s contains %d monkeys"; printf($format,$num,$location); We now have a problem. The order of the placeholders in the format string does not match the order of the arguments in the code. We would like to leave the code as is and simply indicate in the format string which arguments the placeholders refer to. We would write the format string like this instead: $format = "The %2\$s contains %1\$d monkeys"; printf($format,$num,$location); An added benefit here is that you can repeat the placeholders without adding more arguments in the code. For example: $format = "The %2\$s contains %1\$d monkeys. That's a nice %2\$s full of %1\$d monkeys."; printf($format,$num,$location); See also: printf, sscanf, fscanf, and number_format. $isodate = sprintf("%04d-%02d-%02d", $year, $month, $day); $money1 = 68.75; $money2 = 54.35; $money = $money1 + $money2; // echo $money will output "123.1"; $formatted = sprintf("%01.2f", $money); // echo $formatted will output "123.10" strncasecmp Binary safe case-insensitive string comparison of the first n characters int strncasecmp string str1 string str2 int len This function is similar to strcasecmp, with the difference that you can specify the (upper limit of the) number of characters (len) from each string to be used in the comparison. If any of the strings is shorter than len, then the length of that string will be used for the comparison. Returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal. See also ereg, strcasecmp, strcmp, substr, stristr, and strstr. strcasecmp Binary safe case-insensitive string comparison int strcasecmp string str1 string str2 Returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal. $var1 = "Hello"; $var2 = "hello"; if (!strcasecmp($var1, $var2)) { echo '$var1 is equal to $var2 in a case-insensitive string comparison'; } See also ereg, strcmp, substr, stristr, strncasecmp, and strstr. strchr Find the first occurrence of a character string strchr string haystack string needle This function is an alias for strstr, and is identical in every way. strcmp Binary safe string comparison int strcmp string str1 string str2 Returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal. Note that this comparison is case sensitive. See also ereg, strcasecmp, substr, stristr, strncasecmp, strncmp, and strstr. strcoll Locale based string comparison int strcoll string str1 string str2 Returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal. strcoll uses the current locale for doing the comparisons. If the current locale is C or POSIX, this function is equivalent to strcmp. Note that this comparison is case sensitive, and unlike strcmp this function is not binary safe. Added in PHP 4.0.5. See also ereg, strcmp, strcasecmp, substr, stristr, strncasecmp, strncmp, strstr, and setlocale. strcspn Find length of initial segment not matching mask int strcspn string str1 string str2 Returns the length of the initial segment of str1 which does not contain any of the characters in str2. See also strspn. strip_tags Strip HTML and PHP tags from a string string strip_tags string str string allowable_tags This function tries to return a string with all HTML and PHP tags stripped from a given str. It errors on the side of caution in case of incomplete or bogus tags. It uses the same tag stripping state machine as the fgetss function. You can use the optional second parameter to specify tags which should not be stripped. Allowable_tags was added in PHP 3.0.13, PHP4B3. stripcslashes Un-quote string quoted with addcslashes string stripcslashes string str Returns a string with backslashes stripped off. Recognizes C-like \n, \r ..., octal and hexadecimal representation. Added in PHP4b3-dev. See also addcslashes. stripslashes Un-quote string quoted with addslashes string stripslashes string str Returns a string with backslashes stripped off. (\' becomes ' and so on.) Double backslashes are made into a single backslash. See also addslashes. stristr Case-insensitive strstr string stristr string haystack string needle Returns all of haystack from the first occurrence of needle to the end. needle and haystack are examined in a case-insensitive manner. If needle is not found, returns &false;. If needle is not a string, it is converted to an integer and applied as the ordinal value of a character. See also strchr, strrchr, substr, and ereg. strlen Get string length int strlen string str Returns the length of string. strnatcmp String comparisons using a "natural order" algorithm int strnatcmp string str1 string str2 This function implements a comparison algorithm that orders alphanumeric strings in the way a human being would, this is described as a "natural ordering". An example of the difference between this algorithm and the regular computer string sorting algorithms (used in strcmp) can be seen below: $arr1 = $arr2 = array("img12.png","img10.png","img2.png","img1.png"); echo "Standard string comparison\n"; usort($arr1,"strcmp"); print_r($arr1); echo "\nNatural order string comparison\n"; usort($arr2,"strnatcmp"); print_r($arr2); The code above will generate the following output: Standard string comparison Array ( [0] => img1.png [1] => img10.png [2] => img12.png [3] => img2.png ) Natural order string comparison Array ( [0] => img1.png [1] => img2.png [2] => img10.png [3] => img12.png ) For more information see: Martin Pool's Natural Order String Comparison page. Similar to other string comparison functions, this one returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal. Note that this comparison is case sensitive. See also ereg, strcasecmp, substr, stristr, strcmp, strncmp, strncasecmp, strnatcasecmp, strstr, natsort and natcasesort. strnatcasecmp Case insensitive string comparisons using a "natural order" algorithm int strnatcasecmp string str1 string str2 This function implements a comparison algorithm that orders alphanumeric strings in the way a human being would. The behaviour of this function is similar to strnatcmp, except that the comparison is not case sensitive. For more infomation see: Martin Pool's Natural Order String Comparison page. Similar to other string comparison functions, this one returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal. See also ereg, strcasecmp, substr, stristr, strcmp, strncmp, strncasecmp, strnatcmp, and strstr. strncmp Binary safe string comparison of the first n characters int strncmp string str1 string str2 int len This function is similar to strcmp, with the difference that you can specify the (upper limit of the) number of characters (len) from each string to be used in the comparison. If any of the strings is shorter than len, then the length of that string will be used for the comparison. Returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal. Note that this comparison is case sensitive. See also ereg, strncasecmp, strcasecmp, substr, stristr, strcmp, and strstr. str_pad Pad a string to a certain length with another string string str_pad string input int pad_length string pad_string int pad_type This functions returns the input string padded on the left, the right, or both sides to the specified padding length. If the optional argument pad_string is not supplied, the input is padded with spaces, otherwise it is padded with characters from pad_string up to the limit. Optional argument pad_type can be STR_PAD_RIGHT, STR_PAD_LEFT, or STR_PAD_BOTH. If pad_type is not specified it is assumed to be STR_PAD_RIGHT. If the value of pad_length is negative or less than the length of the input string, no padding takes place. $input = "Alien"; print str_pad($input, 10); // produces "Alien " print str_pad($input, 10, "-=", STR_PAD_LEFT); // produces "-=-=-Alien" print str_pad($input, 10, "_", STR_PAD_BOTH); // produces "__Alien___" strpos Find position of first occurrence of a string int strpos string haystack string needle int offset Returns the numeric position of the first occurrence of needle in the haystack string. Unlike the strrpos, this function can take a full string as the needle parameter and the entire string will be used. If needle is not found, returns &false;. It is easy to mistake the return values for "character found at position 0" and "character not found". Here's how to detect the difference: // in PHP 4.0b3 and newer: $pos = strpos($mystring, "b"); if ($pos === false) { // note: three equal signs // not found... } // in versions older than 4.0b3: $pos = strpos($mystring, "b"); if (is_string($pos) && !$pos) { // not found... } If needle is not a string, it is converted to an integer and applied as the ordinal value of a character. The optional offset parameter allows you to specify which character in haystack to start searching. The position returned is still relative to the the beginning of haystack. See also strrpos, strrchr, substr, stristr, and strstr. strrchr Find the last occurrence of a character in a string string strrchr string haystack string needle This function returns the portion of haystack which starts at the last occurrence of needle and goes until the end of haystack. Returns &false; if needle is not found. If needle contains more than one character, the first is used. If needle is not a string, it is converted to an integer and applied as the ordinal value of a character. // get last directory in $PATH $dir = substr(strrchr($PATH, ":"), 1); // get everything after last newline $text = "Line 1\nLine 2\nLine 3"; $last = substr(strrchr($text, 10), 1 ); See also strchr, substr, stristr, and strstr. str_repeat Repeat a string string str_repeat string input int multiplier Returns input_str repeated multiplier times. multiplier has to be greater than 0. echo str_repeat("-=", 10); This will output "-=-=-=-=-=-=-=-=-=-=". This function was added in PHP 4.0. strrev Reverse a string string strrev string string Returns string, reversed. strrpos Find position of last occurrence of a char in a string int strrpos string haystack char needle Returns the numeric position of the last occurrence of needle in the haystack string. Note that the needle in this case can only be a single character. If a string is passed as the needle, then only the first character of that string will be used. If needle is not found, returns &false;. It is easy to mistake the return values for "character found at position 0" and "character not found". Here's how to detect the difference: // in PHP 4.0b3 and newer: $pos = strrpos($mystring, "b"); if ($pos === false) { // note: three equal signs // not found... } // in versions older than 4.0b3: $pos = strrpos($mystring, "b"); if (is_string($pos) && !$pos) { // not found... } If needle is not a string, it is converted to an integer and applied as the ordinal value of a character. See also strpos, strrchr, substr, stristr, and strstr. strspn Find length of initial segment matching mask int strspn string str1 string str2 Returns the length of the initial segment of str1 which consists entirely of characters in str2. The line of code: $var = strspn("42 is the answer, what is the question ...", "1234567890"); will assign 2 to $var, because the string "42" will be the longest segment containing characters from "1234567890". See also strcspn. strstr Find first occurrence of a string string strstr string haystack string needle Returns all of haystack from the first occurrence of needle to the end. If needle is not found, returns &false;. If needle is not a string, it is converted to an integer and applied as the ordinal value of a character. Note that this function is case-sensitive. For case-insensitive searches, use stristr. $email = 'sterling@designmultimedia.com'; $domain = strstr($email, '@'); print $domain; // prints @designmultimedia.com See also strchr, stristr, strrchr, substr, and ereg. strtok Tokenize string string strtok string arg1 string arg2 strtok is used to tokenize a string. That is, if you have a string like "This is an example string" you could tokenize this string into its individual words by using the space character as the token. $string = "This is an example string"; $tok = strtok($string," "); while ($tok) { echo "Word=$tok<br>"; $tok = strtok(" "); } Note that only the first call to strtok uses the string argument. Every subsequent call to strtok only needs the token to use, as it keeps track of where it is in the current string. To start over, or to tokenize a new string you simply call strtok with the string argument again to initialize it. Note that you may put multiple tokens in the token parameter. The string will be tokenized when any one of the characters in the argument are found. Also be careful that your tokens may be equal to "0". This evaluates to &false; in conditional expressions. See also split and explode. strtolower Make a string lowercase string strtolower string str Returns string with all alphabetic characters converted to lowercase. Note that 'alphabetic' is determined by the current locale. This means that in i.e. the default "C" locale, characters such as umlaut-A (Ä) will not be converted. $str = "Mary Had A Little Lamb and She LOVED It So"; $str = strtolower($str); print $str; # Prints mary had a little lamb and she loved it so See also strtoupper and ucfirst. strtoupper Make a string uppercase string strtoupper string string Returns string with all alphabetic characters converted to uppercase. Note that 'alphabetic' is determined by the current locale. For instance, in the default "C" locale characters such as umlaut-a (δ) will not be converted. $str = "Mary Had A Little Lamb and She LOVED It So"; $str = strtoupper($str); print $str; # Prints MARY HAD A LITTLE LAMB AND SHE LOVED IT SO See also strtolower and ucfirst. str_replace Replace all occurrences of the search string with the replacement string mixed str_replace mixed search mixed replace mixed subject This function returns a string or an array with all occurences of search in subject replaced with the given replace value. If you don't need fancy replacing rules, you should always use this function instead of ereg_replace or preg_replace. In PHP 4.0.5 and later, every parameter to str_replace can be an array. If subject is an array, then the search and replace is performed with every entry of subject, and the return value is an array as well. If search and replace are arrays, then str_replace takes a value from each array and uses them to do search and replace on subject. If replace has fewer values than search, then an empty string is used for the rest of replacement values. If search is an array and replace is a string; then this replacement string is used for every value of search. The converse would not make sense, though. $bodytag = str_replace("%body%", "black", "<body text=%body%>"); This function is binary safe. str_replace was added in PHP 3.0.6, but was buggy up until PHP 3.0.8. See also ereg_replace, preg_replace, and strtr. strtr Translate certain characters string strtr string str string from string to This function returns a copy of str, translating all occurrences of each character in from to the corresponding character in to and returning the result. If from and to are different lengths, the extra characters in the longer of the two are ignored. $addr = strtr($addr, "δεφ", "aao"); strtr can be called with only two arguments. If called with two arguments it behaves in a new way: from then has to be an array that contains string -> string pairs that will be replaced in the source string. strtr will always look for the longest possible match first and will *NOT* try to replace stuff that it has already worked on. Examples: $trans = array("hello" => "hi", "hi" => "hello"); echo strtr("hi all, I said hello", $trans) . "\n"; This will show: "hello all, I said hi", This feature (two arguments) was added in PHP 4.0. See also ereg_replace. substr Return part of a string string substr string string int start int length Substr returns the portion of string specified by the start and length parameters. If start is positive, the returned string will start at the start'th position in string, counting from zero. For instance, in the string 'abcdef', the character at position 0 is 'a', the character at position 2 is 'c', and so forth. Examples: $rest = substr("abcdef", 1); // returns "bcdef" $rest = substr("abcdef", 1, 3); // returns "bcd" If start is negative, the returned string will start at the start'th character from the end of string. Examples: $rest = substr("abcdef", -1); // returns "f" $rest = substr("abcdef", -2); // returns "ef" $rest = substr("abcdef", -3, 1); // returns "d" If length is given and is positive, the string returned will end length characters from start. If this would result in a string with negative length (because the start is past the end of the string), then the returned string will contain the single character at start. If length is given and is negative, the string returned will end length characters from the end of string. If this would result in a string with negative length, then the returned string will contain the single character at start. Examples: $rest = substr("abcdef", 1, -1); // returns "bcde" See also strrchr and ereg. substr_count Count the number of substring occurrences int substr_count string haystrack string needle substr_count returns the number of times the needle substring occurs in the haystack string. print substr_count("This is a test", "is"); // prints out 2 substr_replace Replace text within a portion of a string string substr_replace string string string replacement int start int length substr_replace replaces a copy of string delimited by the start and (optionally) length parameters with the string given in replacement. The result is returned. If start is positive, the replacing will begin at the start'th offset into string. If start is negative, the replacing will begin at the start'th character from the end of string. If length is given and is positive, it represents the length of the portion of string which is to be replaced. If it is negative, it represents the number of characters from the end of string at which to stop replacing. If it is not given, then it will default to strlen( string ); i.e. end the replacing at the end of string. <?php $var = 'ABCDEFGH:/MNRPQR/'; echo "Original: $var<hr>\n"; /* These two examples replace all of $var with 'bob'. */ echo substr_replace($var, 'bob', 0) . "<br>\n"; echo substr_replace($var, 'bob', 0, strlen($var)) . "<br>\n"; /* Insert 'bob' right at the beginning of $var. */ echo substr_replace($var, 'bob', 0, 0) . "<br>\n"; /* These next two replace 'MNRPQR' in $var with 'bob'. */ echo substr_replace($var, 'bob', 10, -1) . "<br>\n"; echo substr_replace($var, 'bob', -7, -1) . "<br>\n"; /* Delete 'MNRPQR' from $var. */ echo substr_replace($var, '', 10, -1) . "<br>\n"; ?> See also str_replace and substr. substr_replace was added in PHP 4.0. trim Strip whitespace from the beginning and end of a string string trim string str string charlist This function returns a string with whitespace stripped from the beginning and end of str. Without the second parameter, trim will strip these characters: " " (ASCII 32 (0x20)), an ordinary space. "\t" (ASCII 9 (0x09)), a tab. "\n" (ASCII 13 (0x0D)), a newline. "\r" (ASCII 10 (0x0A)), a return. "\0" (ASCII 0 (0x00)), the NUL-byte. "\x0B" (ASCII 11 (0x0B)), a . You can also specify the characters you want to strip, by means of the charlist parameter. Simply list all characters that you want to be stripped. With .. you can specify a range of characters. ]]> The second parameter was added in PHP 4.0.7 See also ltrim and rtrim. ucfirst Make a string's first character uppercase string ucfirst string str Returns a string with the first character of str capitalized, if that character is alphabetic. Note that 'alphabetic' is determined by the current locale. For instance, in the default "C" locale characters such as umlaut-a (ä) will not be converted. $text = 'mary had a little lamb and she loved it so.'; $text = ucfirst($text); // $text is now Mary had a little lamb // and she loved it so. See also strtoupper and strtolower. ucwords Uppercase the first character of each word in a string string ucwords string str Returns a string with the first character of each word in str capitalized, if that character is alphabetic. $text = "mary had a little lamb and she loved it so."; $text = ucwords($text); // $text is now: Mary Had A Little // Lamb And She Loved It So. The definition of a word is any string of characters that is immediately after a whitespace (These are: space, form-feed, newline, carriage return, horizontal tab, and vertical tab). See also strtoupper, strtolower and ucfirst. wordwrap Wraps a string to a given number of characters using a string break character. string wordwrap string str int width string break int cut Returns a string with str wrapped at the column number specified by the (optional) width parameter. The line is broken using the (optional) break parameter. wordwrap will automatically wrap at column 75 and break using '\n' (newline) if width or break are not given. If the cut is set to 1, the string is always wrapped at the specified width. So if you have a word that is larger than the given width, it is broken apart. (See second example). The cut parameter was added in PHP 4.0.3. $text = "The quick brown fox jumped over the lazy dog."; $newtext = wordwrap( $text, 20 ); echo "$newtext\n"; This example would display: The quick brown fox jumped over the lazy dog. $text = "A very long woooooooooooord."; $newtext = wordwrap( $text, 8, "\n", 1); echo "$newtext\n"; This example would display: A very long wooooooo ooooord. See also nl2br.