In other words: equality is not intuitive. Awesome!
---
Let's take a look at "how PHP works":
0 == 08 // true!
0 === 08 // also true!
(Sonofabitch/Facepalm) * Infinity
This is just stupid behavior. 08 is an invalid octal sequence, but no error is raised. You can't detect this condition unless you do your own pre-parsing before allowing PHP to try to parse it!
decimal : [1-9][0-9]*
| 0
hexadecimal : 0[xX][0-9a-fA-F]+
octal : 0[0-7]+
integer : [+-]?decimal
| [+-]?hexadecimal
| [+-]?octal
php -r "var_dump(08);"
The bottom line probably is that your literals just shouldn't have leading zeroes…
$v = validated_integer($user_input); // the user input 08
if($v == 0 || $v === 0) { // let's just be safe
// the Wrong Thing happens
}