php man page for version_compare

VERSION_COMPARE(3)							 1							VERSION_COMPARE(3)

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

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

DESCRIPTION
       version_compare(3) compares two "PHP-standardized" version number strings.

	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 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 devel-
       opment state.

PARAMETERS
	      o $version1
		- First version number.

	      o $version2
		- Second version number.

	      o $operator
		-  If  the  third optional $operator argument is specified, test for a particular relationship. The possible operators are: <, lt,
		<=, le, >, gt, >=, ge, ==, =, eq, !=, <>, ne respectively.  This parameter is case-sensitive, values should be lowercase.

RETURN VALUES
	By default, version_compare(3) 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(3) 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 . "
";
	      }

	      if (version_compare(PHP_VERSION, '5.3.0') >= 0) {
		  echo 'I am at least PHP version 5.3.0, my version: ' . PHP_VERSION . "
";
	      }

	      if (version_compare(PHP_VERSION, '5.0.0', '>=')) {
		  echo 'I am using PHP 5, my version: ' . PHP_VERSION . "
";
	      }

	      if (version_compare(PHP_VERSION, '5.0.0', '<')) {
		  echo 'I am using PHP 4, my version: ' . PHP_VERSION . "
";
	      }
	      ?>

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).

       Note

	       Special version strings such as alpha and beta are case sensitive. Version strings from arbitrary sources that do not adhere to the
	      PHP standard may need to be lowercased via strtolower(3) before calling version_compare(3).

SEE ALSO
       phpversion(3), php_uname(3), function_exists(3).

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