Compare version numbers of the format X.Y.Z (major.minor.patch)

version_cmp.php

<?php
/**
*  Compare version numbers of the format X.Y.Z where X,Y,Z are non-negative integers
*  Values with less than three parts will be padded out with zeros, eg. "1.1" becomes "1.1.0", "1" becomes "1.0.0"
*
*  @return 1 if $a is greater (a later version) than $b, 0 if $a is equal to $b, -1 if $a is less (an earlier version) than $b
*
*/
function version_cmp($a, $b) {

    $nums1 = explode('.',$a);
    $nums2 = explode('.',$b);

    $nums1 = array_pad($nums1, 3, '0');
    $nums2 = array_pad($nums2, 3, '0');

    if($nums1[0] < $nums2[0]) {
        // $a is a major version BEHIND
        return -1;
    } else if ($nums1[0] > $nums2[0]) {
        // $a is a major version AHEAD
        return 1;
    } else {

        // major versions are equal
        if ($nums1[1] < $nums2[1]) {
            // $ a is a minor version BEHIND
            return -1;
        } else if ($nums1[1] > $nums2[1]) {
            // $ a is a minor version AHEAD
            return 1;
        } else {

            if ($nums1[2] < $nums2[2]) {
                // $ a is a patch version BEHIND
                return -1;
            } else if ($nums1[2] > $nums2[2]) {
                // $ a is a patch version AHEAD
                return 1;
            } else {
                // version numbers match EXACTLY
                return 0;
            }

        }
    }

}