PHP's variable type leniency

Question

The most recent comment on PHP's in_array() help page (http://uk.php.net/manual/en/function.in-array.php#106319) states that some unusual results occur as a result of PHP's 'leniency on variable types', but gives no explanation as to why these results occur. In particular, I don't follow why these happen:

// Example array

$array = array(
    'egg' => true,
    'cheese' => false,
    'hair' => 765,
    'goblins' => null,
    'ogres' => 'no ogres allowed in this array'
);

// Loose checking (this is the default, i.e. 3rd argument is false), return values are in comments
in_array(763, $array); // true
in_array('hhh', $array); // true

Or why the poster thought the following was strange behaviour

in_array('egg', $array); // true
in_array(array(), $array); // true

(surely 'egg' does occur in the array, and PHP doesn't care whether it's a key or value, and there is an array, and PHP doesn't care if it's empty or not?)

Can anyone give any pointers?

Answer 1

763 == true because true equals anything not 0, NULL or '', same thing for array because it is a value (not an object).

To circumvent this problem you should pass the third argument as TRUE to be STRICT and thus, is_rray will do a === which is a type equality so then

763 !== true

and neither will array() !== true