添加功能的默认参数作为其他功能的结果

Question

Hi I have question it is possible to adding default parameters of the function as result of other function? For example:

static function addParameter(){
return rand(10,100)
}

function doSomething($year=$this->addParameter()) or 
function doSomething($year=class::addParameter()) 

I need to pass actual year and month to my function. When i pass

function($month=3, $year=2016)

it work then but i not want to write this from hand but want to use function or something to always return actual month and year.

Answer 1

Short answer: no, you can't. http://php.net/manual/en/functions.arguments.php states that:

The default value must be a constant expression, not (for example) a variable, a class member or a function call.

You can use default null value (if normally function does not take one) and check if parameter is null, then get value from function:

function testfun($testparam = null) {
    if ($testparam == null) $testparam = myclass::funToReturnParam();
    // Rest of function body
}

Answer 2

Yo can implement it like this

<?php
class Core {
    static function addParameter(){
       return rand(10,100);
    }
}

$core  = new Core();

function doSomething($rand){
    echo 'this is rand '.$rand;
    }

doSomething(Core::addParameter());

You can change the function defination according to your requirement. hope it helps :)

Answer 3

From the PHP Manual (emphasis mine):

The default value must be a constant expression, not (for example) a variable, a class member or a function call.

So only scalar types(boolean, int, string etc), arrays and null are allowed.

A workaround could be to check if the parameter is null and set it within the function:

function doSomething($year = null) {
    if (!$year) {
        $year = addParameter();
    }
    //actually do something
}