Using variables for name and arguments to create a new instance of a class in PHP [duplicate]

Question

I'm trying to call a class function that creates a new instance of a subclass.

I'm doing this inside a foreach loop with the following variables for the sub class name and arguments:

$classname = 'Element_Radio';
$classargs = array( $a, $b ); //Might have up to 4 arguments

Here's the original line of code I'm trying to execute, without any of the above variables:

$form->addElement(new Element_Radio($required, $required, $optional_array, $optional_array);

So first I tried:

$form->addElement( new $classname ($classargs) );

But I think I need something like this:

$form->addElement( call_user_func_array(new $classname,$classargs) );

Either way, I'm getting errors of:

"Warning: Missing argument 2 for Element::__construct() ..."

So it looks like the arguments are getting passed in as one array variable, and not separately.

I ended up writing a bunch of if statements to just make the function call depending on the values of $classargs, but I'm wondering if there is a programmatic way of doing what I want without the IFs.

EDIT - SOLUTION with the code I added to account for the fact that my array of arguments was a multidimensional array that didn't have all numeric indexes. The splat operator (...) only works with an array with numeric indexes.

$classname = 'Element_Radio';
$classargs = array();

if ( isset( $a ) ) { array_push($classargs, $a); }
if ( isset( $b ) ) { array_push($classargs, $b); }
if ( isset( $c ) ) { array_push($classargs, $c); }
if ( isset( $d ) ) { array_push($classargs, $d); }

$form->addElement( new $classname ( ...$classargs ) );

deceze · Accepted Answer · 2017-03-09 20:13:23Z

5

Either use the argument unpacking operator ...:

new $classname(...$classargs)

Or reflection:

(new ReflectionClass($classname))->newInstanceArgs($classargs)

edited Mar 9, 2017 at 20:13

answered Mar 9, 2017 at 20:06

deceze♦

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3 Comments

AbraCadaver Over a year ago

variadic function operator is in the function definition, that is argument unpacking or splat

deceze Over a year ago

Ah right. It doesn't really seem to have an official name besides "... token", which makes it a bit hard to talk about.

Michelle Over a year ago

I ended up using the edited code above for anyone who gets here via search.

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