php is null when empty? [duplicate]
As is shown in the following table, empty($foo) is equivalent to $foo==null and is_null($foo) has the same function of $foo===null. The table also shows some tricky values regarding the null comparison. (ϕ denotes an uninitialized variables. )
empty is_null ==null ===null isset array_key_exists ϕ | T | T | F | F null | T | T | F | T "" | T | F | T | T [] | T | F | T | T 0 | T | F | T | T false | T | F | T | T true | F | F | T | T 1 | F | F | T | T \0 | F | F | T | T