php-doc-en/reference/mcrypt/functions/mdecrypt-generic.xml

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  <refentry id="function.mdecrypt-generic">
   <refnamediv>
    <refname>mdecrypt_generic</refname>
    <refpurpose>This function decrypts data</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>string</type><methodname>mdecrypt_generic</methodname>
      <methodparam><type>resource</type><parameter>td</parameter></methodparam>
      <methodparam><type>string</type><parameter>data</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function decrypts data. Note that the length of the
     returned string can in fact be longer then the unencrypted
     string, due to the padding of the data.
    </para>
    <para>
     <example>
      <title><function>mdecrypt_generic</function> Example</title>
      <programlisting role="php">
<![CDATA[
<?php
$iv_size = mcrypt_enc_get_iv_size ($td));
$iv = @mcrypt_create_iv ($iv_size, MCRYPT_RAND);

if (@mcrypt_generic_init ($td, $key, $iv) != -1)
{
    $c_t = mcrypt_generic ($td, $plain_text);
    @mcrypt_generic_init ($td, $key, $iv);
    $p_t = mdecrypt_generic ($td, $c_t);
}
if (strncmp ($p_t, $plain_text, strlen($plain_text)) == 0)
    echo "ok";
else
    echo "error";
?>
]]>
      </programlisting>
      <para>
       The above example shows how to check if the data before the
       encryption is the same as the data after the decryption.
      </para>
     </example>
    </para>
   </refsect1>
  </refentry>

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