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 re

Answer 1

Internally, you can think of the basic in_array() call working like this:

function in_array($needle, $haystack, $strict = FALSE) {
    foreach ($haystack as $key => $value) {
        if ($strict === FALSE) {
            if ($value == $needle) {
                return($key);
            }
        } else {
            if ($value === $needle) {
                return($key);
        }
    }
    return(FALSE);
}

note that it's using the == comparison operator - this one allows typecasting. So if your array contains a simple boolean TRUE value, then essentially EVERYTHING your search for with in_array will be found, and almost everything EXCEPT the following in PHP can be typecast as true:

'' == TRUE // false
0 == TRUE // false
FALSE == TRUE // false
array() == TRUE // false
'0' == TRUE // false

but:

'a' == TRUE // true
1 == TRUE // true
'1' == TRUE // true
3.1415926 = TRUE // true
etc...

This is why in_array has the optional 3rd parameter to force a strict comparison. It simply makes in_array do a === strict comparison, instead of ==.

Which means that

'a' === TRUE // FALSE