true, false, and null

• Booleans (true and false) are to be used when possible, rather than numeric equivalents

Incorrect:

    if($foo) $bar = 1;

Correct:

    if($foo) $bar = true;

• ! should be used when possible vs function calls

Incorrect:

    if(empty($str)) $str = 'stuff';

Correct:

    if(!$str) $str = 'stuff';