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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@215274 c90b9560-bf6c-de11-be94-00142212c4b1
88 lines
2.9 KiB
XML
88 lines
2.9 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.9 $ -->
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<!-- splitted from ./en/functions/misc.xml, last change in rev 1.2 -->
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<refentry id="function.uniqid">
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<refnamediv>
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<refname>uniqid</refname>
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<refpurpose>Generate a unique ID</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<methodsynopsis>
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<type>string</type><methodname>uniqid</methodname>
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<methodparam choice="opt"><type>string</type><parameter>prefix</parameter></methodparam>
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<methodparam choice="opt"><type>bool</type><parameter>more_entropy</parameter></methodparam>
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</methodsynopsis>
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<simpara>
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<function>uniqid</function> returns a prefixed unique identifier
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based on the current time in microseconds. <parameter>prefix</parameter>
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became optional in PHP 5 but can be useful, for instance, if you generate identifiers
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simultaneously on several hosts that might happen to generate the
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identifier at the same microsecond. Up until PHP 4.3.1,
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<parameter>prefix</parameter> could only be a maximum of 114
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characters long.
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</simpara>
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<simpara>
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If the optional <parameter>more_entropy</parameter> parameter is
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&true;, <function>uniqid</function> will add additional entropy (using
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the combined linear congruential generator) at the end of the return
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value, which should make the results more unique.
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</simpara>
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<simpara>
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With an empty <parameter>prefix</parameter>, the returned string
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will be 13 characters long. If <parameter>more_entropy</parameter> is
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&true;, it will be 23 characters.
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</simpara>
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<note>
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<simpara>
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The <parameter>prefix</parameter> parameter is required before PHP 5.
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</simpara>
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</note>
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<para>
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If you need a unique identifier or token and you intend to give
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out that token to the user via the network (i.e. session cookies),
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it is recommended that you use something along these lines:
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</para>
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<para>
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<informalexample>
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<programlisting role="php">
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<![CDATA[
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<?php
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// no prefix
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// works only in PHP 5 and later versions
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$token = md5(uniqid());
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// better, difficult to guess
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$better_token = md5(uniqid(rand(), true));
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?>
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]]>
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</programlisting>
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</informalexample>
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</para>
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<simpara>
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This will create a 32 character identifier (a 128 bit hex number)
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that is extremely difficult to predict.
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</simpara>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"../../../../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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