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

Answer 1

‘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.