unserialize.xml

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<refentry xml:id="function.unserialize" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>unserialize</refname>
  <refpurpose>
   Creates a PHP value from a stored representation
  </refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>mixed</type><methodname>unserialize</methodname>
   <methodparam><type>string</type><parameter>str</parameter></methodparam>
   <methodparam choice="opt"><type>array</type><parameter>options</parameter></methodparam>
  </methodsynopsis>
  <simpara>
   <function>unserialize</function> takes a single serialized variable and
   converts it back into a PHP value.  
  </simpara>
  <warning>
   <para>
    Do not pass untrusted user input to <function>unserialize</function> regardless
    of the <parameter>options</parameter> value of <literal>allowed_classes</literal>.
    Unserialization can result in code being loaded and executed due to object
    instantiation and autoloading, and a malicious user may be able to exploit
    this. Use a safe, standard data interchange format such as JSON (via
    <function>json_decode</function> and <function>json_encode</function>) if
    you need to pass serialized data to the user.
   </para>
   <para>
    If you need to unserialize externally-stored serialized data, consider using
    <function>hash_hmac</function> for data validation. Make sure data is
    not modified by anyone but you.
   </para>
  </warning>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>str</parameter></term>
     <listitem>
      <para>
       The serialized string.
      </para>
      <para>
       If the variable being unserialized is an object, after successfully 
       reconstructing the object PHP will automatically attempt to call the
       <link linkend="object.wakeup">__wakeup()</link> member
       function (if it exists).
      </para>
      <para>
       <note>
        <title>unserialize_callback_func directive</title>
        <para>
         It's possible to set a callback-function which will be called,
         if an undefined class should be instantiated during unserializing.
         (to prevent getting an incomplete <type>object</type> "__PHP_Incomplete_Class".)
         Use your &php.ini;, <function>ini_set</function> or &htaccess; 
         to define <link linkend="ini.unserialize-callback-func">unserialize_callback_func</link>.
         Everytime an undefined class should be instantiated, it'll be called.  To disable this feature just
         empty this setting.
        </para>
       </note>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>options</parameter></term>
     <listitem>
      <para>
       Any options to be provided to <function>unserialize</function>, as an
       associative array.
      </para>
      <table>
       <title>Valid options</title>
       <tgroup cols="3">
        <thead>
         <row>
          <entry>Name</entry>
          <entry>Type</entry>
          <entry>Description</entry>
         </row>
        </thead>
        <tbody>
         <row>
          <entry><literal>allowed_classes</literal></entry>
          <entry><type>mixed</type></entry>
          <entry>
           <simpara>
            Either an <type>array</type> of class names which should be
            accepted, &false; to accept no classes, or &true; to accept all
            classes. If this option is defined and
            <function>unserialize</function> encounters an object of a class
            that isn't to be accepted, then the object will be instantiated as
            <classname>__PHP_Incomplete_Class</classname> instead.
           </simpara>
           <simpara>
            Omitting this option is the same as defining it as &true;: PHP
            will attempt to instantiate objects of any class.
           </simpara>
          </entry>
         </row>
        </tbody>
       </tgroup>
      </table>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The converted value is returned, and can be a <type>boolean</type>,
   <type>integer</type>, <type>float</type>, <type>string</type>,
   <type>array</type> or <type>object</type>.
  </para>
  <para>
   In case the passed string is not unserializeable, &false; is returned and
   <constant>E_NOTICE</constant> is issued.
  </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>7.1.0</entry>
       <entry>
        The <literal>allowed_classes</literal> element of
        <parameter>options</parameter>) is now strictly typed, i.e. if anything
        other than an <type>array</type> or a <type>boolean</type> is given,
        <function>unserialize</function> returns &false; and issues an
        <constant>E_WARNING</constant>.
       </entry>
      </row>
      <row>
       <entry>7.0.0</entry>
       <entry>
        The <parameter>options</parameter> parameter has been added.
       </entry>
      </row>
      <row>
       <entry>5.6.0</entry>
       <entry>
        Manipulating the serialised data by replacing <literal>C:</literal>
        with <literal>O:</literal> to force object instantiation without
        calling the constructor will now fail.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>unserialize</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
// Here, we use unserialize() to load session data to the
// $session_data array from the string selected from a database.
// This example complements the one described with serialize().

$conn = odbc_connect("webdb", "php", "chicken");
$stmt = odbc_prepare($conn, "SELECT data FROM sessions WHERE id = ?");
$sqldata = array($_SERVER['PHP_AUTH_USER']);
if (!odbc_execute($stmt, $sqldata) || !odbc_fetch_into($stmt, $tmp)) {
    // if the execute or fetch fails, initialize to empty array
    $session_data = array();
} else {
    // we should now have the serialized data in $tmp[0].
    $session_data = unserialize($tmp[0]);
    if (!is_array($session_data)) {
        // something went wrong, initialize to empty array
        $session_data = array();
    }
}
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title>unserialize_callback_func example</title>
    <programlisting role="php">
<![CDATA[
<?php
$serialized_object='O:1:"a":1:{s:5:"value";s:3:"100";}';

ini_set('unserialize_callback_func', 'mycallback'); // set your callback_function

function mycallback($classname) 
{
    // just include a file containing your classdefinition
    // you get $classname to figure out which classdefinition is required
}
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <warning>
   <para>
    &false; is returned both in the case of an error and if unserializing
    the serialized &false; value. It is possible to catch this special case by
    comparing <parameter>str</parameter> with
    <literal>serialize(false)</literal> or by catching the issued
    <constant>E_NOTICE</constant>.
   </para>
  </warning>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>json_encode</function></member>
    <member><function>json_decode</function></member>
    <member><function>hash_hmac</function></member>
    <member><function>serialize</function></member>
    <member><link linkend="language.oop5.autoload">Autoloading Classes</link></member>
    <member><link linkend="ini.unserialize-callback-func">unserialize_callback_func</link></member>
    <member><link linkend="object.wakeup">__wakeup()</link></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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