Passing a boolean through PHP GET

Question

Pretty simple question here, not sure the answer though. Can I pass a boolean variable through get? For example:

http://example.com/foo.php?myVar=true

then I have

$hopefullyBool = $_GET['myVar'];

Is $hopefullyBool a boolean or a string? My hypothesis is that it's a string but can someone let me know? Thanks

Answer 1

All GET parameters will be strings in PHP. Use filter_var and FILTER_VALIDATE_BOOLEAN:

Returns TRUE for "1", "true", "on" and "yes". Returns FALSE otherwise.

If FILTER_NULL_ON_FAILURE is set, FALSE is returned only for "0", "false", "off", "no", and "", and NULL is returned for all non-boolean values.

$hopefullyBool = filter_var($_GET['myVar'], FILTER_VALIDATE_BOOLEAN);

Another way to get the type boolean, pass as something that evaluates to true or false like 0 or 1:

http://example.com/foo.php?myVar=0
http://example.com/foo.php?myVar=1

Then cast to boolean:

$hopefullyBool = (bool)$_GET['myVar'];

If you want to pass string true or false then another way:

$hopefullyBool = $_GET['myVar'] == 'true' ? true : false;

But I would say that filter_var with FILTER_VALIDATE_BOOLEAN was meant for this.

Answer 2

If you want to avoid an if statement:

filter_var('true', FILTER_VALIDATE_BOOLEAN);  
//bool(true)

filter_var('false', FILTER_VALIDATE_BOOLEAN); 
//bool(false)

Answer 3

It would be passed as a string. While you can convert it using the bool cast, it is recommended to not do so in some cases.

You would be better off doing if myVar == "True"

Be cautious:

>>> bool("foo")
True
>>> bool("")
False

Empty strings evaluate to False, but everything else evaluates to True. So this should not be used for any kind of parsing purposes.

Answer 4

There's a few ways to do it. Firstly we could use PHP's in-built (boolean) method, which casts a string value to a boolean:

$hopefullyBool = (boolean)$_GET['myVar'];

This would result in a boolean value of true or false depending on the value of the string in $_GET['myVar'].

From v5.2.1 upwards, we can also use json_decode() to ascertain the boolean value:

$hopefullyBool = json_decode($_GET['myVar]);

The json_decode() method parses a JSON Object (which is a string) into a PHP variable, and takes type-casting into account. As a result, the string 'true' from the URL param will be cast to the boolean true.

You could use both of the above methods in tandem, using:

$hopefullyBool = (boolean)json_decode($_GET['myVar]);

To mitigate against uppercase characters being passed in the URL param (eg ?myVar=True or ?myVar=FALSE), you should use the strtolower() method, which will convert a string to all lowercase letters:

$hopefullyBool = (boolean)json_decode(strtolower($_GET['myVar]));

Finally, we'll want to fall-back to false if the parameter is not present in the URL's query string, otherwise PHP will throw an Undefined Index notice. To do this, we can use the isset() method:

$hopefullyBool = false;
if ( isset($_GET['myVar']) ) {
    $hopefullyBool = (boolean)json_decode(strtolower($_GET['myVar]));
}

To shorten this, you could initiate $hopefullyBool using a conditional statement like so:

$hopefullyBool = isset($_GET['myVar']) && (boolean)json_decode(strtolower($_GET['myVar']));