php-doc-en/reference/strings/functions/crc32.xml

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<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.crc32">
 <refnamediv>
  <refname>crc32</refname>
  <refpurpose>Calculates the crc32 polynomial of a string</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>int</type><methodname>crc32</methodname>
   <methodparam><type>string</type><parameter>str</parameter></methodparam>
  </methodsynopsis>
  <para>
   Generates the cyclic redundancy checksum polynomial of 32-bit
   lengths of the <parameter>str</parameter>. This is usually used
   to validate the integrity of data being transmitted.
  </para>
  <para>
   Because PHP's integer type is signed, and many crc32 checksums will
   result in negative integers, you need to use the "%u" formatter of
   <function>sprintf</function> or <function>printf</function> to get
   the string representation of the unsigned crc32 checksum.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>str</parameter></term>
     <listitem>
      <para>
       The data.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Displaying a crc32 checksum</title>
    <para>
     This example shows how to print a converted checksum with the
     <function>printf</function> function:
    </para>
    <programlisting role="php">
<![CDATA[
<?php
$checksum = crc32("The quick brown fox jumped over the lazy dog.");
printf("%u\n", $checksum);
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>md5</function></member>
    <member><function>sha1</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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