php-doc-en/reference/mbstring/functions/mb-substr.xml

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<refentry xml:id="function.mb-substr" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>mb_substr</refname>
  <refpurpose>Get part of string</refpurpose>
 </refnamediv>
   
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>mb_substr</methodname>
   <methodparam><type>string</type><parameter>str</parameter></methodparam>
   <methodparam><type>int</type><parameter>start</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>length</parameter><initializer>NULL</initializer></methodparam>
   <methodparam choice="opt"><type>string</type><parameter>encoding</parameter><initializer>mb_internal_encoding()</initializer></methodparam>
  </methodsynopsis>
  <para>
   Performs a multi-byte safe
   <function>substr</function> operation based on
   number of characters. Position is
   counted from the beginning of
   <parameter>str</parameter>. First character's position is
   0. Second character position is 1, and so on. 
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>str</parameter></term>
     <listitem>
      <para>
       The <type>string</type> to extract the substring from.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>start</parameter></term>
     <listitem>
      <para>
       If <parameter>start</parameter> is non-negative, the returned string
       will start at the <parameter>start</parameter>'th position in
       <parameter>str</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>
      <para>
       If <parameter>start</parameter> is negative, the returned string
       will start at the <parameter>start</parameter>'th character
       from the end of <parameter>str</parameter>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>length</parameter></term>
     <listitem>
      <para>
       Maximum number of characters to use from <parameter>str</parameter>. If
       omitted or <literal>NULL</literal> is passed, extract all characters to
       the end of the string.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>encoding</parameter></term>
     <listitem>
      &mbstring.encoding.parameter;
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   <function>mb_substr</function> returns the portion of
   <parameter>str</parameter> specified by the
   <parameter>start</parameter> and
   <parameter>length</parameter> parameters.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>5.4.8</entry>
       <entry>
        Passing <literal>NULL</literal> as <parameter>length</parameter>
        extracts all characters to the end of the string. Prior to this version
        <literal>NULL</literal> was treated the same as <literal>0</literal>.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>mb_strcut</function></member>
    <member><function>mb_internal_encoding</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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