script stops when require_once(dirname(dirname(dirname(dirname(dirname(__FILE__))))).'/lib/Cake/bootstrap.php'); line gets executed

Question

I am using CakePHP 2.8x . In webroot I am calling a php which needs to require

require_once(dirname(dirname(dirname(dirname(dirname(__FILE__))))).'/lib/Cake/bootstrap.php');

My script gets executed till this line. From this line the script halts without producing any error. I tried

if ( file_exists(dirname(dirname(dirname(dirname(dirname(__FILE__))))).'/lib/Cake/bootstrap.php')){
    echo "file exits";
    require_once(dirname(dirname(dirname(dirname(dirname(__FILE__))))).'/lib/Cake/bootstrap.php');
    echo "file ";
}
else{
    echo "file not found";
}

Here I get file exists but donot get file

Then I tried

if (!require_once(dirname(dirname(dirname(dirname(dirname(__FILE__))))).'/lib/Cake/bootstrap.php')){
    echo "file included";
}
else{
    echo "file not included";
}

but here I don't get any output here.