Consider these 2 examples

$key = 'jim';

// example 1
    if (isset($array[$key])) {
       doWhatIWant();
    }

// example 2    
    if (array_key_exists($key, $array)) {
       doWhatIWant();
    }

I'm interested in knowing if either of these are better. I've always used the first, but have seen a lot of people use the second example on this site.

So, which is better? Faster? Clearer intent?

Update

Thanks for the quality answers. I now understand the difference between the 2. A benchmark states that isset() alone is quicker than array_key_exists(). However, if you want the isset() to behave like array_key_exists() it is slower.