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<refentry xml:id="function.trim" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>trim</refname> 
  <refpurpose>Strip whitespace (or other characters) from the beginning and end of a string</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>trim</methodname>
   <methodparam><type>string</type><parameter>string</parameter></methodparam>
   <methodparam choice="opt"><type>string</type><parameter>characters</parameter><initializer>" \n\r\t\v\0"</initializer></methodparam>
  </methodsynopsis>
  <para>
   This function returns a string with whitespace stripped from the
   beginning and end of <parameter>string</parameter>.
   Without the second parameter,
   <function>trim</function> will strip these characters:
   <!-- sorted by importance. Printed 3 times: trim, ltrim, rtrim -->
   <itemizedlist>
    <listitem>
     <simpara>
      " " (<acronym>ASCII</acronym> <literal>32</literal> 
      (<literal>0x20</literal>)), an ordinary space.
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      "\t" (<acronym>ASCII</acronym> <literal>9</literal> 
      (<literal>0x09</literal>)), a tab.
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      "\n" (<acronym>ASCII</acronym> <literal>10</literal> 
      (<literal>0x0A</literal>)), a new line (line feed).
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      "\r" (<acronym>ASCII</acronym> <literal>13</literal> 
      (<literal>0x0D</literal>)), a carriage return.
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      "\0" (<acronym>ASCII</acronym> <literal>0</literal> 
      (<literal>0x00</literal>)), the <literal>NUL</literal>-byte.
     </simpara>
    </listitem>
    <listitem>
     <simpara> <!-- not \v, since not supported by PHP -->
      "\x0B" (<acronym>ASCII</acronym> <literal>11</literal> 
      (<literal>0x0B</literal>)), a vertical tab.
     </simpara>
    </listitem>
   </itemizedlist>
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>string</parameter></term>
     <listitem>
      <para>
       The <type>string</type> that will be trimmed.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>characters</parameter></term>
     <listitem>
      <para>
       Optionally, the stripped characters can also be specified using
       the <parameter>characters</parameter> parameter.
       Simply list all characters that you want to be stripped. With
       <literal>..</literal> you can specify a range of characters.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The trimmed string.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Usage example of <function>trim</function></title>
    <programlisting role="php">
<![CDATA[
<?php

$text   = "\t\tThese are a few words :) ...  ";
$binary = "\x09Example string\x0A";
$hello  = "Hello World";
var_dump($text, $binary, $hello);

print "\n";

$trimmed = trim($text);
var_dump($trimmed);

$trimmed = trim($text, " \t.");
var_dump($trimmed);

$trimmed = trim($hello, "Hdle");
var_dump($trimmed);

$trimmed = trim($hello, 'HdWr');
var_dump($trimmed);

// trim the ASCII control characters at the beginning and end of $binary
// (from 0 to 31 inclusive)
$clean = trim($binary, "\x00..\x1F");
var_dump($clean);

?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
string(32) "        These are a few words :) ...  "
string(16) "    Example string
"
string(11) "Hello World"

string(28) "These are a few words :) ..."
string(24) "These are a few words :)"
string(5) "o Wor"
string(9) "ello Worl"
string(14) "Example string"
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title>Trimming array values with <function>trim</function></title>
    <programlisting role="php">
<![CDATA[
<?php
function trim_value(&$value) 
{ 
    $value = trim($value); 
}

$fruit = array('apple','banana ', ' cranberry ');
var_dump($fruit);

array_walk($fruit, 'trim_value');
var_dump($fruit);

?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
array(3) {
  [0]=>
  string(5) "apple"
  [1]=>
  string(7) "banana "
  [2]=>
  string(11) " cranberry "
}
array(3) {
  [0]=>
  string(5) "apple"
  [1]=>
  string(6) "banana"
  [2]=>
  string(9) "cranberry"
}

]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <title>Possible gotcha: removing middle characters</title>
   <para>
    Because <function>trim</function> trims characters from the beginning and end of
    a <type>string</type>, it may be confusing when characters are (or are not) removed from
    the middle. <literal>trim('abc', 'bad')</literal> removes both 'a' and 'b' because it
    trims 'a' thus moving 'b' to the beginning to also be trimmed. So, this is why it "works"
    whereas <literal>trim('abc', 'b')</literal> seemingly does not.
   </para>
  </note>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>ltrim</function></member>
    <member><function>rtrim</function></member>
    <member><function>str_replace</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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