Gitlab Hook auto deploy live web server

gitlab.php

<?php
// CONFIG

// This token must sent with the request, for security
$TOKEN='XXXXXXXXXXX';
$LOCAL_GIT=realpath(dirname(__DIR__) . '/app.git');
$PRODUCTION_DIR=realpath(dirname(__DIR__) . '/public_html');

$REMOTE = 'origin';
$LOCAL_BRANCH = 'master';

$LOG_FILE = __DIR__ . '/log.txt';

date_default_timezone_set("Asia/Jakarta");
set_time_limit(0);

$log_handle = fopen($LOG_FILE, 'a');

if( !$log_handle )
{
	die('FATAL ERROR CANNOT OPEN LOG FILE');
}

function write_log($msg){
	global $log_handle;
	return fwrite($log_handle, rtrim( $msg ) . "\n" );
}



// Log separator
fwrite($log_handle, str_repeat('-', 10) . ' START ' . 
				date('Y-m-d H:i:s') . ' ' .  str_repeat('-', 10) . "\n" );
$request_token = @$_SERVER['HTTP_X_GITLAB_TOKEN'];
write_log('User: ' . shell_exec('whoami'));
write_log('Client: ' . @$_SERVER["HTTP_USER_AGENT"]);

if(!function_exists('shell_exec'))
{
	write_log("ERROR: no shell_exec function.");
	header("HTTP/1.0 500 Internal Error");
	exit;
}

$GIT = shell_exec('which git');
if(empty($GIT)) {
	write_log("ERROR: No git binary found.");
	header("HTTP/1.0 500 Internal Error");
	exit;
}


if( ! $LOCAL_GIT ){
	write_log("ERROR: Invalid local repo dir.");
	header("HTTP/1.0 500 Internal Error");
	exit;	
}

if( ! $PRODUCTION_DIR ){
	write_log("ERROR: Invalid prod dir.");
	header("HTTP/1.0 500 Internal Error");
	exit;	
}


if( $request_token !== $TOKEN ){
	write_log("ERROR: Invalid token " . $request_token);
	header("HTTP/1.0 403 Forbidden");
	exit;
}

// Change work dir to local GIT repo
chdir($LOCAL_GIT);

write_log('Fetching remote..');
$result = shell_exec('git fetch ' . $REMOTE . ' 2>&1');
write_log($result);

write_log('Cleaning local changes..');
$result = shell_exec('git stash drop');
write_log($result);

write_log('Updating files into production..');
$result = shell_exec('GIT_WORK_TREE="' . $PRODUCTION_DIR . '" git pull -f 2>&1');
write_log($result);


$result = shell_exec($cmd);
write_log($result);

fwrite($log_handle, str_repeat('-', 10) . ' DONE ' . 
				date('Y-m-d H:i:s') . ' ' .  str_repeat('-', 10) . "\n" );

fclose($log_handle);