Did you try with a relative adresse?
$my_file = 'site/file.txt';
Question
when I run my page on my local host it does not create the file. I have given read and write permissions to the folder site. i have used system and exec functions and when i run the page via the terminal it creates a file but via my browser it doesnt.
$my_file = '/var/www/site/file.txt';
$handle = fopen($my_file, 'w') or die('Cannot open file: '.$my_file);
Solution 2
Did you try with a relative adresse?
$my_file = 'site/file.txt';
OTHER TIPS
The following commands will correctly apply permissions to the directory.
cd /var/www/site
sudo chmod 664 *
sudo find . -type d -exec chmod 755 {} \;
If the error persists, please post any PHP errors that are thrown.