[stewart]

<?php

$file = implode('', file('mylist.txt'));

for($i = 0; $i < strlen($file); $i++) {
	if($file[$i] == "b"){
		die("for good.");
	}
}

?>

That does what you are asking, but what are you trying to accomplish, just wondering ?

http://www.php.net/file
http://www.php.net/strlen
http://www.php.net/implode

Good luck,
- Stewart
link removed