function isFile($ext){
    $ext = strtolower($ext);
    $f = array( 'application/zip', 'application/x-zip-compressed', 'application/octet-stream', 'application/x-zip-compressed' );
    $f_ext = array( 'zip', 'ZIP' );
    if( in_array($_FILES["file"]["type"], $f) && in_array($ext, $f_ext)){
        return true;
    }
}