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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@9920 c90b9560-bf6c-de11-be94-00142212c4b1
321 lines
10 KiB
Text
321 lines
10 KiB
Text
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<reference id="ref.regex">
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<title>Regular expression functions</title>
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<titleabbrev>Regexps</titleabbrev>
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<partintro>
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<para>
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Regular expressions are used for complex string manipulation in
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PHP. The functions that support regular expressions are:
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<itemizedlist>
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<listitem>
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<simpara><function>ereg</function>
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</listitem>
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<listitem>
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<simpara><function>ereg_replace</function>
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</listitem>
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<listitem>
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<simpara><function>eregi</function>
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</listitem>
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<listitem>
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<simpara><function>eregi_replace</function>
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</listitem>
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<listitem>
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<simpara><function>split</function>
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</listitem>
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</itemizedlist>
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These functions all take a regular expression string as their
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first argument. PHP uses the POSIX extended regular expressions
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as defined by POSIX 1003.2. For a full description of POSIX
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regular expressions see the regex man pages included in the regex
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directory in the PHP distribution.
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<!-- Should add discussion of PCRE functions here. -->
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<para>
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<example>
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<title>Regular expression examples</title>
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<programlisting>
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ereg("abc",$string);
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/* Returns true if "abc"
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is found anywhere in $string. */
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ereg("^abc",$string);
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/* Returns true if "abc"
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is found at the beginning of $string. */
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ereg("abc$",$string);
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/* Returns true if "abc"
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is found at the end of $string. */
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eregi("(ozilla.[23]|MSIE.3)",$HTTP_USER_AGENT);
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/* Returns true if client browser
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is Netscape 2, 3 or MSIE 3. */
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ereg("([[:alnum:]]+) ([[:alnum:]]+) ([[:alnum:]]+)",
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$string,$regs);
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/* Places three space separated words
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into $regs[1], $regs[2] and $regs[3]. */
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$string = ereg_replace("^","<BR>",$string);
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/* Put a <BR> tag at the beginning of $string. */
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$string = ereg_replace("$","<BR>",$string);
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/* Put a <BR> tag at the end of $string. */
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$string = ereg_replace("\n","",$string);
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/* Get rid of any carriage return
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characters in $string. */
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</programlisting>
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</example>
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</partintro>
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<refentry id="function.ereg">
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<refnamediv>
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<refname>ereg</refname>
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<refpurpose>regular expression match</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcdef>int <function>ereg</function></funcdef>
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<paramdef>string <parameter>pattern</parameter></paramdef>
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<paramdef>string <parameter>string</parameter></paramdef>
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<paramdef>array <parameter><optional>regs</optional></parameter></paramdef>
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</funcsynopsis>
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<simpara>
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Searchs <parameter>string</parameter> for matches to the regular expression
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given in <parameter>pattern</parameter>.
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<simpara>
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If matches are found for parenthesized substrings of
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<parameter>pattern</parameter> and the function is called with
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the third argument <parameter>regs</parameter>, the matches will
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be stored in the elements of
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<parameter>regs</parameter>. $regs[1] will contain the substring
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which starts at the first left parenthesis; $regs[2] will contain the
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substring starting at the second, and so on. $regs[0] will
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contain a copy of <parameter>string</parameter>.
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<para>
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Searching is case sensitive.
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<para>
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Returns true if a match for pattern was found in string, or false
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if no matches were found or an error occurred.
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<para>
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The following code snippet takes a date in ISO format (YYYY-MM-DD)
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and prints it in DD.MM.YYYY format:
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<example>
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<title>ereg() example</title>
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<programlisting>
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if ( ereg( "([0-9]{4})-([0-9]{1,2})-([0-9]{1,2})", $date, $regs ) ) {
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echo "$regs[3].$regs[2].$regs[1]";
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} else {
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echo "Invalid date format: $date";
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}
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</programlisting></example>
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<para>
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See also <function>eregi</function>, <function>ereg_replace</function>, and <function>eregi_replace</function>.
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</refsect1>
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</refentry>
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<refentry id="function.ereg-replace">
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<refnamediv>
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<refname>ereg_replace</refname>
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<refpurpose>replace regular expression</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcdef>string <function>ereg_replace</function></funcdef>
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<paramdef>string <parameter>pattern</parameter></paramdef>
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<paramdef>string <parameter>replacement</parameter></paramdef>
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<paramdef>string <parameter>string</parameter></paramdef>
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</funcsynopsis>
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<para>
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This function scans <parameter>string</parameter> for matches to
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<parameter>pattern</parameter>, then replaces the matched text
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with <parameter>replacement</parameter>.
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<para>
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The modified string is returned. (Which may mean that the
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original string is returned if there are no matches to be
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replaced.)
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<para>
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If <parameter>pattern</parameter> contains parenthesized
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substrings, <parameter>replacement</parameter> may contain
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substrings of the form
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<literal>\\<replaceable>digit</replaceable></literal>, which will
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be replaced by the text matching the digit'th parenthesized
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substring; <literal>\\0</literal> will produce the entire
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contents of string. Up to nine substrings may be used.
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Parentheses may be nested, in which case they are counted by the
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opening parenthesis.
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<para>
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If no matches are found in <parameter>string</parameter>, then
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<parameter>string</parameter> will be returned unchanged.
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<para>
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For example, the following code snippet
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prints "This was a test" three times:
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<example>
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<title>ereg_replace() example</title>
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<programlisting>
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$string = "This is a test";
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echo ereg_replace( " is", " was", $string );
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echo ereg_replace( "( )is", "\\1was", $string );
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echo ereg_replace( "(( )is)", "\\2was", $string );
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</programlisting>
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</example>
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<para>
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See also <function>ereg</function>, <function>eregi</function>,
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and <function>eregi_replace</function>.
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</refsect1>
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</refentry>
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<refentry id="function.eregi">
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<refnamediv>
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<refname>eregi</refname>
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<refpurpose>case insensitive regular expression match</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcdef>int <function>eregi</function></funcdef>
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<paramdef>string <parameter>pattern</parameter></paramdef>
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<paramdef>string <parameter>string</parameter></paramdef>
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<paramdef>array <parameter><optional>regs</optional></parameter></paramdef>
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</funcsynopsis>
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<para>
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This function is identical to <function>ereg</function> save that this ignores
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case distinction when matching alphabetic characters.
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<para>
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See also <function>ereg</function>, <function>ereg_replace</function>, and <function>eregi_replace</function>.
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</refsect1>
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</refentry>
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<refentry id="function.eregi-replace">
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<refnamediv>
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<refname>eregi_replace</refname>
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<refpurpose>replace regular expression case insensitive</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcdef>string <function>eregi_replace</function></funcdef>
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<paramdef>string <parameter>pattern</parameter></paramdef>
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<paramdef>string <parameter>replacement</parameter></paramdef>
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<paramdef>string <parameter>string</parameter></paramdef>
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</funcsynopsis>
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<para>
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This function is identical to <function>ereg_replace</function> save that
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this ignores case distinction when matching alphabetic characters.
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<para>
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See also <function>ereg</function>, <function>eregi</function>, and <function>ereg_replace</function>.
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</refsect1>
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</refentry>
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<refentry id="function.split">
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<refnamediv>
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<refname>split</refname>
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<refpurpose>split string into array by regular expression</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcdef>array <function>split</function></funcdef>
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<paramdef>string <parameter>pattern</parameter></paramdef>
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<paramdef>string <parameter>string</parameter></paramdef>
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<paramdef>int <parameter><optional>limit</optional></parameter></paramdef>
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</funcsynopsis>
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<para>
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Returns an array of strings, each of which is a substring of
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string formed by splitting it on boundaries formed
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by <parameter>pattern</parameter>. If an error occurs, returns false.
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<para>
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To get the first five fields from a line from
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<filename>/etc/passwd</filename>:
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<example>
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<title>split() example</title>
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<programlisting>
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$passwd_list = split( ":", $passwd_line, 5 );
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</programlisting></example>
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<para>
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Note that <parameter>pattern</parameter> is case-sensitive.
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<para>
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See also: <function>explode</function> and <function>implode</function>.
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</refsect1>
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</refentry>
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<refentry id="function.sql-regcase">
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<refnamediv>
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<refname>sql_regcase</refname>
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<refpurpose>make regular expression for case insensitive match</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<funcsynopsis>
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<funcdef>string <function>sql_regcase</function></funcdef>
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<paramdef>string <parameter>string</parameter></paramdef>
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</funcsynopsis>
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<para>
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Returns a valid regular expression which will match <parameter>string</parameter>,
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ignoring case. This expression is <parameter>string</parameter> with each character
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converted to a bracket expression; this bracket expression
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contains that character's uppercase and lowercase form if
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applicable, otherwise it contains the original character
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twice.
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<example>
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<title>sql_regcase() example</title>
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<programlisting>
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echo sql_regcase( "Foo bar" );
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</programlisting></example>
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prints <screen>[Ff][Oo][Oo][ ][Bb][Aa][Rr]</screen>.
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<para>
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This can be used to achieve case insensitive pattern matching in
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products which support only case sensitive regular expressions.
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</refsect1>
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</refentry>
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</reference>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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-->
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