这个PHP做什么?它是编码器/解码器吗?

我一点也不懂PHP,这更像是一个好奇的问题。

在文本文件中,下面的php函数后面是几千个字符的文本,例如:

xnEFstUhSNWGSx5zTq4X/AUw/rtism+klrBETWg0xE1uwb49rnRxrgrgY5EEp3Y0uvTcvLqhUFOP
4n7LDLQpQ9UACTyuUjGBKmUScQCYLCP08u06t0K3nWTNiM7Q6bQMk/iZBE+UK1ywbVC1Lzr9OOEK

这个php函数是否将随机查找的文本编码成php?加密方案可以从中得到解决吗?

编辑: 客户表示他拥有由他人开发的代码的全部所有权和权利。如何解码?需要密码吗?

<?php //003ac
if (!extension_loaded('ionCube Loader')) {
    $__oc = strtolower(substr(php_uname(), 0, 3));
    $__ln = 'ioncube_loader_' . $__oc . '_' . substr(phpversion(), 0, 3) . (($__oc == 'win') ? '.dll' : '.so');
    @dl($__ln);
    if (function_exists('_il_exec')) {
        return _il_exec();
    }
    $__ln   = '/ioncube/' . $__ln;
    $__oid  = $__id = realpath(ini_get('extension_dir'));
    $__here = dirname(__FILE__);
    if (strlen($__id) > 1 && $__id[1] == ':') {
        $__id   = str_replace('\\', '/', substr($__id, 2));
        $__here = str_replace('\\', '/', substr($__here, 2));
    }
    $__rd = str_repeat('/..', substr_count($__id, '/')) . $__here . '/';
    $__i  = strlen($__rd);
    while ($__i--) {
        if ($__rd[$__i] == '/') {
            $__lp = substr($__rd, 0, $__i) . $__ln;
            if (file_exists($__oid . $__lp)) {
                $__ln = $__lp;
                break;
            }
        }
    }
    @dl($__ln);
} else {
    die('The file ' . __FILE__ . " is corrupted.\n");
}
if (function_exists('_il_exec')) {
    return _il_exec();
}
echo ('Site error: the file <b>' . __FILE__ . '</b> requires the ionCube 
PHP Loader ' . basename($__ln) . '  to be installed by the site administrator.');
exit(199);
?>