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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.10 $ -->
<!-- splitted from ./en/functions/info.xml, last change in rev 1.2 -->
<refentry id="function.version-compare">
<refnamediv>
<refname>version_compare</refname>
<refpurpose>
Compares two "PHP-standardized" version number strings
</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<methodsynopsis>
<type>mixed</type><methodname>version_compare</methodname>
<methodparam><type>string</type><parameter>version1</parameter></methodparam>
<methodparam><type>string</type><parameter>version2</parameter></methodparam>
<methodparam choice="opt"><type>string</type><parameter>
operator
</parameter></methodparam>
</methodsynopsis>
<para>
<function>version_compare</function> compares two
"PHP-standardized" version number strings. This is useful if you
would like to write programs working only on some versions of
PHP.
</para>
<para>
<function>version_compare</function> returns -1 if the first
version is lower than the second, 0 if they are equal, and +1 if
the second is lower.
</para>
<para>
The function first replaces <literal>_</literal>, <literal>-</literal>
and <literal>+</literal> with a dot <literal>.</literal> in the version
strings and also inserts dots <literal>.</literal> before and after any
non number so that for example '4.3.2RC1' becomes '4.3.2.RC.1'. Then it
splits the results like if you were using explode('.', $ver). Then it
compares the parts starting from left to right. If a part contains
special version strings these are handled in the following order:
<literal>dev</literal> < <literal>alpha</literal> =
<literal>a</literal> < <literal>beta</literal> =
<literal>b</literal> < <literal>RC</literal> <
<literal>pl</literal>. This way not only versions with different levels
like '4.1' and '4.1.2' can be compared but also any PHP specific version
containing development state.
</para>
<para>
If you specify the third optional <parameter>operator</parameter>
argument, you can test for a particular relationship. The
possible operators are: <literal><</literal>,
<literal>lt</literal>, <literal><=</literal>,
<literal>le</literal>, <literal>></literal>,
<literal>gt</literal>, <literal>>=</literal>,
<literal>ge</literal>, <literal>==</literal>,
<literal>=</literal>, <literal>eq</literal>,
<literal>!=</literal>, <literal><></literal>,
<literal>ne</literal> respectively. Using this argument, the
function will return &true; if the relationship is the one specified
by the operator, &false; otherwise.
</para>
<note>
<para>
<constant>PHP_VERSION</constant> constant holds current PHP version.
</para>
</note>
<para>
<example>
<title><function>version_compare</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// prints -1
echo version_compare("4.0.4", "4.0.6");
// these all print 1
echo version_compare("4.0.4", "4.0.6", "<");
echo version_compare("4.0.6", "4.0.6", "eq");
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
</refentry>
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