filesize() function to determine the size of a file on the hard disk
this function takes a filename as an argument
filesize( “myfile.txt” )
This returns the size of the specified file in bytes, or false upon error
Example of filesize() in php
<?php
// outputs e.g. somefile.txt: 1024 bytes
$filename = 'somefile.txt';
echo $filename . ': ' . filesize($filename) . ' bytes';
?>