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

<?xml version="1.0" encoding="utf-8"?>
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<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.strpos">
 <refnamediv>
  <refname>strpos</refname>
  <refpurpose>Find the position of the first occurrence of a substring in a string</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>int</type><methodname>strpos</methodname>
   <methodparam><type>string</type><parameter>haystack</parameter></methodparam>
   <methodparam><type>mixed</type><parameter>needle</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>offset</parameter><initializer>0</initializer></methodparam>
  </methodsynopsis>
  <para>
   Find the numeric position of the first occurrence of
   <parameter>needle</parameter> in the <parameter>haystack</parameter> string.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>haystack</parameter></term>
     <listitem>
      <para>
       The string to search in.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>needle</parameter></term>
     <listitem>
      <para>
       If <parameter>needle</parameter> is not a string, it is converted
       to an integer and applied as the ordinal value of a character.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>offset</parameter></term>
     <listitem>
      <para>
       If specified, search will start this number of characters counted from
       the beginning of the string. Unlike <function>strrpos</function> and
       <function>strripos</function>, the offset cannot be negative.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the position of where the needle exists relative to the beginning of
   the <parameter>haystack</parameter> string (independent of offset).
   Also note that string positions start at 0, and not 1.
  </para>
  <para>
   Returns &false; if the needle was not found.
  </para>
  &return.falseproblem;
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Using <literal>===</literal></title>
    <programlisting role="php">
<![CDATA[
<?php
$mystring = 'abc';
$findme   = 'a';
$pos = strpos($mystring, $findme);

// Note our use of ===.  Simply == would not work as expected
// because the position of 'a' was the 0th (first) character.
if ($pos === false) {
    echo "The string '$findme' was not found in the string '$mystring'";
} else {
    echo "The string '$findme' was found in the string '$mystring'";
    echo " and exists at position $pos";
}
?>
]]>
    </programlisting>
   </example>

   <example>
    <title>Using !==</title>
    <programlisting role="php">
<![CDATA[
<?php
$mystring = 'abc';
$findme   = 'a';
$pos = strpos($mystring, $findme);

// The !== operator can also be used.  Using != would not work as expected
// because the position of 'a' is 0. The statement (0 != false) evaluates 
// to false.
if ($pos !== false) {
     echo "The string '$findme' was found in the string '$mystring'";
         echo " and exists at position $pos";
} else {
     echo "The string '$findme' was not found in the string '$mystring'";
}
?>
]]>
    </programlisting>
   </example>

   <example>
    <title>Using an offset</title>
    <programlisting role="php">
<![CDATA[
<?php
// We can search for the character, ignoring anything before the offset
$newstring = 'abcdef abcdef';
$pos = strpos($newstring, 'a', 1); // $pos = 7, not 0
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  &note.bin-safe;
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>stripos</function></member>
    <member><function>strrpos</function></member>
    <member><function>strripos</function></member>
    <member><function>strstr</function></member>
    <member><function>strpbrk</function></member>
    <member><function>substr</function></member>
    <member><function>preg_match</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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