The usage of === in PHP

[Melindrea]

@traq

I think we were quite off-topic in that post, but I think the discussion is good =)

So, to recap, the difference between `==` (or `!=`) and `===` (or `!==`) is that the second one also tests type, so for instance (to use your exact example):

$i = 0;
// == does type coercion. FALSE and 0 are equivalent…
if ($i == false) { /* true! */ }
// …but NOT identical.
if ($i === false) { /* false! */ }

// real-world example:
$str = “ABCDEFG”;
// you hate the letter “A”.
// make sure $str DOES NOT HAVE the letter “A” in it!
if (strpos($str,”A”) == false) {
// this compares as TRUE, even though “A” is in the string!
// this is because the *first* position in the string is position *0*.
// 0 == false.
}

// same example, but using ===
if (strpos($str,”A”) === false) {
// this compares as FALSE, as expected.
// 0 !== false.
}

So, outside of most people not being aware of the difference, are there any downsides to using `===`/`!==`?

[unasAquila]

There are some down sides where integers such as `(8 === 08)` would return false but `( 7 === 07)` would return true.
Which is due to integers beginning with 0 being interpreted as an octal.
As with the `(8 === 08)` case `8 it would actually === 010`.
Just a small caveat but can cause issues if not known about.

[__]

> So, outside of most people not being aware of the difference, are there any downsides to using `===`/`!==`?

`==` is a leading cause of logical *(referring to the programmer’s logic, not the parser’s)* comparison errors. In most cases, using `===` yields the same (intended) result without the risk of any unintended consequences.

Yes, there are certainly times when you *want* to do type coercion – maybe , for example:

// say we asked the user, “what is 2 + 2?”
// and they wrote “4” in the answer box:
$answer = $_POST;

// we check it:
if( $answer === 4 ){
// however, HTTP POST values are always strings,
// so this will not compare as TRUE.
}

// two solutions:
// explicitly cast $answer as an integer
if( (int)$answer === 4 ){
// works perfectly
// some people will tell you this is the *best* approach
// (and they’re not wrong, really)
}

// …or, you can allow PHP to do type coercion on its own
if( $answer == 4 ){
// works just fine
// easier for coding kiddies to understand
}

…however, in my experience (both in my own programming, and in helping others), the difficulties when this *doesn’t* work far outweigh any benefits gained when it *does* work. Especially since this sort of flaw can work as intended *most of the time* (i.e., it doesn’t *always* break things. Broken things should *always* break).

*****
> There are some down sides where integers such as (8 === 08) would return false but ( 7 === 07) would return true. Which is due to integers beginning with 0 being interpreted as an octal. As with the (8 === 08) case 8 it would actually === 010. Just a small caveat but can cause issues if not known about.
— @unasAquila

In your example, `(7 == 07)` and `(7 === 07)` are both true (as is `(7 == ’07’)`, but not `(7 === ’07’)`), while `(8 == 08)` and `(8 === 08)` are both false. Decimal and octal numbers are both integers in PHP; just different ways of writing them. Using `==` or `===` isn’t the problem here, it’s writing `08` when you really meant `8`. But yes, it’s certainly one of those obscure, frustrating behaviors!

[unasAquila]

in php i would do something like.

$num = 08;
$int = (int)ltrim($num, ‘0’);

Javascript however doesn’t seem to have the problem.

[CrocoDillon]

If you expect an int from user input, the input will probably be a string.

$num = ’08’;
$int = (int)ltrim($num, ‘0’);

> (on a sidenote, casting the string 08 to int does turn it into the decimal number 8)

Seems a bit obsolete then :p

[__]

> Of course, looking closer at it, that’s because it appears to be set to 0 immediately.

That’s because octal (base **8**) uses the digits 0-7. `08` is invalid, and so produces `0`.

@unasAquila, treating an octal number as a string won’t work as expected. Even though you typed `08`, PHP doesn’t store the number that way. This is not because `08` is invalid – try it with a valid octal number and you’ll see the same thing:

print strval( 014 );
// outputs “12”, not “014”

[Author]

Posts