Php insert text into file at marker taken from http://www.learncomputer.com/php-insert-text-into-file-at-position/

gistfile1.txt

/**
* Insert arbitrary text into any place inside a text file
*
* @param string $file_path - absolute path to the file
* @param string $insert_marker - a marker inside the file to 
*	look for as a pattern match
* @param string $text - text to be inserted
* @param boolean $after - whether to insert text after (true) 
*	or before (false) the marker. By default, the text is 
*	inserted after the marker.
* @return integer - the number of bytes written to the file
*/
function insert_into_file($file_path, $insert_marker, 
		$text, $after = true) {
	$contents = file_get_contents($file_path);
	$new_contents = preg_replace($insert_marker, 
			($after) ? '$0' . $text : $text . '$0', $contents);
	return file_put_contents($file_path, $new_contents);
}

$file_path = "/var/www/myapp/my_file";
$insert_marker = "#### INSERT TEXT MARKER ####";
$text = "\nI am a PHP inserted text!!!";

$num_bytes = insert_into_file($file_path, $insert_marker, $text, true);

if ($num_bytes === false) {
	echo "Could not insert into file $file_path.";
} else {
	echo "Insert successful!";
}