php function's required parameter confusion

Question

I am looking for the exact type of a Required Parameter in a PHP Function signature

Does initializing a parameter only with NULL makes it an optional? i.e

function foo($optional=NULL, $OptionalOrRequired="Optional Or Required", $required){}

I am confused about the 2nd argument, does it comes in Required or Optional parameter?

UPDATE

I am using reflection to get all and required parameters of a function

public function getPlayer($params=3, $c){}
// results
$reflection->getNumberOfParameters()            ->   2
$reflection->getNumberOfRequiredParameters()    ->   2 // it should be one

public function getPlayer($params=3, $c, $x=NULL)
// results
$reflection->getNumberOfParameters()            ->   3
$reflection->getNumberOfRequiredParameters()    ->   2

As i get in one answer that defaults comes before required, is this the reason the reflection function is returning wrong count for required parameters?

Thanks

Basically, you omit the right hand side of the parameter from the function declaration, i.e = null then it's required, otherwise if not supplied, the parameter assumes the default value you specified on the right of the parameter declaration. — Gavin
– Gavin, Commented May 30, 2012 at 10:07
thanks for a quick reply Gavin, am actually confused about this NULL vs actual value that i used in 2nd parameter. in the given method signature is 2nd parameter optional or required? — Junaid
– Junaid, Commented May 30, 2012 at 10:10
Optional, as you have provided the default value for it, should the user not provide a value when calling it. — Gavin
– Gavin, Commented May 30, 2012 at 10:16

connec · Accepted Answer · 2012-05-30 10:26:56Z

'Optional' arguments are just arguments with a default value, whether that value is null, false, a string (etc.) does not matter - if a function argument has a default value it is optional.

However, it wouldn't make sense to have an optional parameter come before a required parameter, as you must give the prior arguments some value (even if it's null) in order to 'get to' the required argument - so all arguments before the last 'required' argument are effectively required.

Some examples:

// Bad
function bad($optional = 'literally anything', $required) {}

bad('required arg');              // This breaks - 'missing argument 2'
bad('something', 'required arg'); // This works - both parameters are needed

// Good
function($required, $optional = 'literally anything') {}

good('required arg');              // This works just fine, last argument has a default
good('required arg', 'something'); // Also works fine, overrides 'literally anything'

Update RE: Reflection

As noted above, putting an 'optional' parameter before a required parameter effectively makes that 'optional' parameter required, as a value must be given for it in order to ever satisfy the method signature.

For example, if the first argument has a default and second argument does not (like in the bad function above), we NEED to pass a second argument, and so we NEED to pass a first argument also, so both are 'required'. If there are subsequent arguments with default values, still only the first 2 arguments are required.

lanzz · Accepted Answer · 2012-05-30 10:08:30Z

1

You cannot have a required parameter coming after optional parameters in PHP. The optional parameters always have to follow the required ones (if any). Any parameter that has a default value provided (e.g. $param = 'default') is optional and any parameter without a default value is required.

answered May 30, 2012 at 10:08

lanzz

43.4k12 gold badges93 silver badges99 bronze badges

Comments

Gavin · Accepted Answer · 2012-05-30 10:08:37Z

-1

Further to my comment.

function test($required, $optional = null)
{

}

test(); // throws an error stating $required is missing
test('a'); // sets $required to 'a' and $optional is null
test('a', 'b'); // sets $required to 'a' and $optional to 'b'

answered May 30, 2012 at 10:08

Gavin

6,3695 gold badges32 silver badges39 bronze badges

1 Comment

Kayla Over a year ago

This is not what the OP is talking about. He is confused about a function whose optional arguments come first, and then the required arguments. Ex: function test($optional = null, $required)

Collectives™ on Stack Overflow

php function's required parameter confusion

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related