About php : php-not-able-to-write-file-on-ubuntu-EC2-instance

Error:

The file temp/71076cc.php is not writable

Code (compiler.php):

$random = substr(md5(mt_rand()), 0, 7);
$filePath = "temp/" . $random . ".php";
if (is_writable($filePath)) {
    if (!$fp = fopen($filePath, 'a')) {
         echo "Cannot open file ($filename)";
         exit;
    }
    if (fwrite($fp, $code) === FALSE) {
        echo "Cannot write to file ($filePath)";
        exit;
    }
    echo "Success, wrote ($code) to file ($filePath)";
    fclose($fp);
} else {
    echo "The file $filePath is not writable";
}

Dir structure of ide directory inside which is inside /var/www/html:

.
├── app
│   ├── compiler.php
│   ├── temp
│   │   ├── a9211d0.php
│   │   └── c7d561e.php
│   └── test.php
└── ui
    ├── css
    │   └── style.css
    ├── ide.html
    └── js
        ├── ide.js
        └── lib

Things I tried:

1. Changing ownership to www-data :

sudo chown -R www-data:www-data /var/www/html/ide/

2. Changing permission to directory:

sudo chmod -R 777 /var/www/html/ide/

3. Changing user which apache uses (in /etc/apache2/envvars):

export APACHE_RUN_USER=ubuntu
export APACHE_RUN_GROUP=ubuntu

as well as

export APACHE_RUN_USER=www-data
export APACHE_RUN_GROUP=www-data

(Both doesnt work)

Kindly suggest any more tweaks to try.

Note:

Currently two files which are seen in temp folder was not made by running compiler.php code. They were made manually. However compiler.php will create such files when called from webserver.