compress js files with php

jscompress.php

<?php

$jsFiles = array(....DEINE JS FILES ...);
$failed = array();
$checksum = "";

foreach($jsFiles as $file){
    $realPath = PIMCORE_DOCUMENT_ROOT . $file;
    if(file_exists($realPath)) {
        $checksum .= ($file . "-" . filemtime($realPath) . "~~");
    } else {
        echo "Failed to load " . $file . " from filesystem - quit.";
        exit;
    }
}

$checksum = md5($checksum);
$cacheFile = PIMCORE_TEMPORARY_DIRECTORY . "/js-cache-" . $checksum . ".js";

if(!file_exists($cacheFile)) {
    $jsContents = "";
    foreach($jsFiles as $file){
        $realPath = PIMCORE_DOCUMENT_ROOT . $file;
        if(file_exists($realPath)) {
            $jsContents .= file_get_contents($realPath) . "\n\n\n\n";
        }
    }
    file_put_contents($cacheFile, $jsContents);
}

?>

<script type="text/javascript" src="<?= str_replace(PIMCORE_DOCUMENT_ROOT, "", $cacheFile); ?>"></script>