Compares two "PHP-standardized" version number strings

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# version_compare

(PHP 4 >= 4.1.0, PHP 5)

version_compare — Compares two "PHP-standardized" version number strings

### Description

mixed version_compare ( string `$version1` , string `$version2` [, string `$operator` ] )

version_compare() compares two "PHP-standardized" version number strings. This is useful if you would like to write programs working only on some versions of PHP.

The function first replaces _, - and + with a dot . in the version strings and also inserts dots . 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: any string not found in this list < dev < alpha = a < beta = b < RC = rc < # < pl = p. 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.

### Parameters

`version1`

  First version number.

`version2`

  Second version number.

`operator`

  If you specify the third optional `operator` argument, you can test for a particular relationship. The possible operators are: <, lt, <=, le, >, gt, >=, ge, ==, =, eq, !=, <>, ne respectively.

  This parameter is case-sensitive, so values should be lowercase.

### Return Values

By default, version_compare() returns -1 if the first version is lower than the second, 0 if they are equal, and 1 if the second is lower.

When using the optional `operator` argument, the function will return `TRUE` if the relationship is the one specified by the operator, `FALSE` otherwise.

### Examples

The examples below use the `PHP_VERSION` constant, because it contains the value of the PHP version that is executing the code.

Example #1 version_compare() examples

`<?php
if (version_compare(PHP_VERSION, '6.0.0') >= 0) {
echo 'I am at least PHP version 6.0.0, my version: ' . PHP_VERSION . "\n";
}
if (version_compare(PHP_VERSION, '5.3.0') >= 0) {
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";
}
?>`

### Notes

> Note: The `PHP_VERSION` constant holds current PHP version.

> Note: Note that pre-release versions, such as 5.3.0-dev, are considered lower than their final release counterparts (like 5.3.0).

### See Also

- phpversion() - Gets the current PHP version
- php_uname() - Returns information about the operating system PHP is running on
- function_exists() - Return TRUE if the given function has been defined

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