php-doc-en/reference/strings/functions/substr.xml

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<!-- $Revision: 1.9 $ -->
<!-- splitted from ./en/functions/strings.xml, last change in rev 1.2 -->
  <refentry id="function.substr">
   <refnamediv>
    <refname>substr</refname>
    <refpurpose>Return part of a string</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>string</type><methodname>substr</methodname>
      <methodparam><type>string</type><parameter>string</parameter></methodparam>
      <methodparam><type>int</type><parameter>start</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>length</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>substr</function> returns the portion of <parameter>string</parameter>
     specified by the <parameter>start</parameter> and
     <parameter>length</parameter> parameters.
    </para>
    <para>
     If <parameter>start</parameter> is non-negative, the returned string
     will start at the <parameter>start</parameter>'th position in
     <parameter>string</parameter>, counting from zero. For instance,
     in the string '<literal>abcdef</literal>', the character at
     position <literal>0</literal> is '<literal>a</literal>', the
     character at position <literal>2</literal> is
     '<literal>c</literal>', and so forth.
    </para>
    <example>
     <title>Basic <function>substr</function> usage</title>
     <programlisting role="php">
<![CDATA[
<?php
$rest = substr("abcdef", 1);    // returns "bcdef"
$rest = substr("abcdef", 1, 3); // returns "bcd"
$rest = substr("abcdef", 0, 4); // returns "abcd"
$rest = substr("abcdef", 0, 8); // returns "abcdef"

// Accessing via curly braces is another option
$string = 'abcdef';
echo $string{0};                // returns a
echo $string{3};                // returns d
?>
]]>
     </programlisting>
    </example>
    <para>
     If <parameter>start</parameter> is negative, the returned string
     will start at the <parameter>start</parameter>'th character
     from the end of <parameter>string</parameter>.
    </para>
    <example>
     <title>Using a negative <parameter>start</parameter></title>
     <programlisting role="php">
<![CDATA[
<?php
$rest = substr("abcdef", -1);    // returns "f"
$rest = substr("abcdef", -2);    // returns "ef"
$rest = substr("abcdef", -3, 1); // returns "d"
?>
]]>
     </programlisting>
    </example>
    <para>
     If <parameter>length</parameter> is given and is positive, the string
     returned will contain at most <parameter>length</parameter> characters
     beginning from <parameter>start</parameter> (depending on the length of
     <parameter>string</parameter>). If <parameter>string</parameter> is less
     than or equal to <parameter>start</parameter> characters long, &false;
     will be returned.
    </para>
    <para>
     If <parameter>length</parameter> is given and is negative, then that many
     characters will be omitted from the end of <parameter>string</parameter>
     (after the start position has been calculated when a
     <parameter>start</parameter> is negative).  If
     <parameter>start</parameter> denotes a position beyond this truncation,
     an empty string will be returned.
    </para>
    <example>
     <title>Using a negative <parameter>length</parameter></title>
     <programlisting role="php">
<![CDATA[
<?php
$rest = substr("abcdef", 0, -1);  // returns "abcde"
$rest = substr("abcdef", 2, -1);  // returns "cde"
$rest = substr("abcdef", 4, -4);  // returns ""
$rest = substr("abcdef", -3, -1); // returns "de"
?>
]]>
     </programlisting>
    </example>
    <para>
     See also <function>strrchr</function>,
     <function>substr_replace</function>,
     <function>ereg</function>,
     <function>trim</function>,
     <function>mb_substr</function> and
     <function>wordwrap</function>.
    </para>
   </refsect1>
  </refentry>

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