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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.14 $ -->
<refentry xml:id="function.version-compare" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>version_compare</refname>
<refpurpose>Compares two "PHP-standardized" version number strings</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<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>
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>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>version1</parameter></term>
<listitem>
<para>
First version number.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>version2</parameter></term>
<listitem>
<para>
Second version number.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>operator</parameter></term>
<listitem>
<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.
</para>
<para>
This parameter is case-sensitive, so values should be lowercase.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
By default, <function>version_compare</function> returns
<literal>-1</literal> if the first version is lower than the second,
<literal>0</literal> if they are equal, and
<literal>1</literal> if the second is lower.
</para>
<para>
When using the optional <parameter>operator</parameter> argument, the
function will return &true; if the relationship is the one specified
by the operator, &false; otherwise.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
The examples below use the <constant>PHP_VERSION</constant> constant,
because it contains the value of the PHP version that is executing
the code.
</para>
<para>
<example>
<title><function>version_compare</function> examples</title>
<programlisting role="php">
<![CDATA[
<?php
if (version_compare(PHP_VERSION, '6.0.0') === 1) {
echo 'I am at least PHP version 6.0.0, my version: ' . PHP_VERSION . "\n";
}
if (version_compare(PHP_VERSION, '5.3.0') === 1) {
echo 'I am at least PHP version 5.3.0, my version: ' . PHP_VERSION . "\n";
}
if (version_compare(PHP_VERSION, '5.0.0', '>')) {
echo 'I am using PHP 5, my version: ' . PHP_VERSION . "\n";
}
if (version_compare(PHP_VERSION, '5.0.0', '<')) {
echo 'I am using PHP 4, my version: ' . PHP_VERSION . "\n";
}
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
<note>
<para>
The <constant>PHP_VERSION</constant> constant holds current PHP version.
</para>
</note>
<note>
<para>
Note that pre-release versions, such as 5.3.0-dev, are considered
lower than their final release counterparts (like 5.3.0).
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>phpversion</function></member>
<member><function>php_uname</function></member>
<member><function>function_exists</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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