quick example of how version_compare works

php-version-check.php

<?php
header('Content-type: text/plain');

$versions = array(
	'1',
	'1.0',
	'1.01',
	'1.1',
	'1.1.0',
	'1.1.1b',
	'1.1.1',
	'1.10',
	'1.10b',
	'1.10.0',
);

$comps = array(
	-1	=> '(below)',
	0	=> '(equal)',
	1	=> '(above)'
);

foreach ( $versions as $version ) {
	if ( isset( $last ) ) {
		$comp	= version_compare( $last, $version );
		echo str_pad( $last, 8, ' ', STR_PAD_LEFT ) . " {$comps[$comp]} {$version}\n";
	}

	$last = $version;
}