I am trying to add random bytes to binary (.exe) files to increase it size using php. So far I got this:

function junk($bs)
{
    // string length: 256 chars
    $tmp = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';

    for($i=0;$i<=$bs;$i++)
    {
        $tmp = $tmp . $tmp;
    }
    return $tmp;
}

$fp = fopen('test.exe', 'ab');
fwrite($fp, junk(1));
fclose($fp);

This works fine and the resulting exe is functional but if I want to do junk(100) to add more size to the file I get the php error "Fatal error: Allowed memory size..."

In which other way could I achieve this without getting an error? Would it be ok to loop the fwrite xxx times?