PHP 自定义版本对比函数

/*
 * 版本比较
 * 返回结果 0< 1= 2>
 *
 * 判断方法
 * <=1 为小于等于
 * >=1 位大于等于
 * =0小于
 * =2为大于
 * =1 为等于
 */
function compare_version($appversion, $lastversion)
{
    $appversion = str_replace('.', '', $appversion);
    $lastversion = str_replace('.', '', $lastversion);
    $alen = strlen($appversion);
    $llen = strlen($lastversion);
    $clen = min($alen, $llen);
    $appversion = substr($appversion, 0, $clen);
    $lastversion = substr($lastversion, 0, $clen);
    if ($appversion < $lastversion) {
        return 0;
    } elseif ($appversion == $lastversion) {
        if ($alen < $llen) {
            return 0;
        } elseif ($alen == $llen) {
            return 1;
        } elseif ($alen > $llen) {
            return 2;
        }
    } elseif ($appversion > $lastversion) {
        return 2;
    }
}