All of these are good answers, but I would like to suggest one more that I feel is a better code standard. You may choose to use a flag in the loop condition that indicates whether or not to continue looping and avoid using break all together.

$arr = array('one', 'two', 'three', 'four', 'stop', 'five');
$length = count($arr);
$found = false;
for ($i = 0; $i < $length && !$found; $i++) {
    $val = $arr[$i];
    if ($val == 'stop') {
        $found = true; // this will cause the code to 
                       // stop looping the next time 
                       // the condition is checked
    }
    echo "$val
\n";
}

I consider this to be better code practice because it does not rely on the scope that break is used. Rather, you define a variable that indicates whether or not to break a specific loop. This is useful when you have many loops that may or may not be nested or sequential.