fwrite() - Binary-safe file write
int fwrite (resource $handle ,string $string [, int $length ]);
fwrite() writes the contents of string to the file stream pointed to by handle.
<?php
$file_name = "c:\folder\resource.txt";
$handle = fopen($file_name, "w");
fwrite($handle, 'Hello');
fwrite($handle, 'World');
fclose($handle);
?>