[Solved] Type-casting to boolean (2024)

php casting boolean

43,681

Solution 1

It's actually not as strange it seems. (bool) has higher precedence than ==, so this:

var_dump((bool) 1==2);

is equivalent to this:

var_dump( ((bool) 1) == 2);

or this:

var_dump(true == 2);

Due to type juggling, the 2 also essentially gets cast to bool (since this is a "loose comparison"), so it's equivalent to this:

var_dump(true == true);

or this:

var_dump(true);

Solution 2

Because in the first example, the cast takes place before the comparison. So it's as if you wrote

((bool) 1)==2

which is equivalent to

true == 2

which is evaluated by converting 2 to true and comparing, ultimately producing true.

To see the expected result you need to add parens to make the order explicit:

var_dump((bool)(1==2));

See it in action.

Solution 3

I use this way:

!!0 (false)!!1 (true)

Solution 4

filter_var - Filters a variable with a specific filter

$boolvar = filter_var('true', FILTER_VALIDATE_BOOLEAN);

boolval - Get the boolean value of a variable PHP 5 >=

$boolvar = boolval ('true');

And literally with a ternary operator but I can't recommend it

$boolvar = ($string === 'true') ? true: false;

View more solutions

43,681

Paris Liakos

Updated on July 09, 2022

Comments

Paris Liakos almost 2 years
Can someone explain me why this:
```
var_dump((bool) 1==2);
```
returns
```
bool(true)
```
but
```
var_dump(1==2);
```
returns
```
bool(false)
```
Of course the second return is correct, but why in the first occasion php returns an unexpected value?
- Brad over 12 years
  
  Order of operations is getting you here...
Paris Liakos over 12 years

Thanks!very detailed explanation:)
Markus Zeller about 8 years

As the headline asks for typecasting this answer is correct and can be used in almost any language. This construct is great for languages like JavaScript where you need a real "true" or "false", but not to keep the original value. BTW, typecasting with (bool) is a little bit faster.
xDaizu over 7 years

...yet another reason to try to always use ===
dougd_in_nc over 6 years

@xDaizu This doesn't have anything to do with using ===. The following returns false, which is still unexpected if you don't understand operator precedence: (bool) 1===1 Simply use == and === when each is appropriate for the given situation. Not just based on some "always do this" rule.
ruakh over 6 years

@dougd_in_nc: You're right that (bool) 1===1 has a similar problem to (bool) 1==2, but === does eliminate half of what's confusing here: the type juggling rules are complicated and counterintuitive. I'm not aware, personally, of any situation where == is appropriate, but I guess that's a matter for a different question . . .
dougd_in_nc over 6 years

@ruakh with regard to the question, I don't find the expression 1==2 confusing at all and I'm aware of several situations where == works very well. Again, == vs. === is irrelevant to finding a solution to the given problem. Type juggling has nothing to do with the problem that the OP is presenting. It's just confusing this with a separate issue.
ruakh over 6 years

@dougd_in_nc: Re: "I don't find the expression 1==2 confusing at all": But the OP's code didn't have the expression 1==2, it had the equivalent of true==2. Do you really claim to find it obvious that true==2 should be true? Re: "I'm aware of several situations where == works very well": Ah, but are you aware of any situations where it's better than ===? If not, then a "never use ==, only ===" rule is actually a pretty good one.
dougd_in_nc over 6 years

The OP code has var_dump((bool) 1==2); It's the equivalent of true == 2 because of the OPERATOR PRECEDENCE. Just like ((bool) 1===1) is equivalent to (true === 1)... That's certainly not obvious the way it's written, even with ===. Also, true==2 isn't hard to understand for me, and makes perfect sense for some applications. However, if anyone doesn't understand == well enough to use it, then I can understand why they would want to always use ===. So, to each his own.
Daniel Wu over 3 years

@dougd_in_nc If OP used === in the first statement, he's going to get bool(false) as he wanted, because true is not the same as 2.
dougd_in_nc over 3 years

@DanielWu yes, you found one of the many ways to change an expression to evaluate false. The poster wasn't asking "how can I make this expression return false." If the poster just wanted to find a way to get false, I'm sure they could do that by themselves