Question

how to get a class constructor function name without instantiating the class?

example:

$class = 'someClass';
$constructor = somehow get constructor;

$args = array();
$object = call_user_func_array(array($class,$constructor),$args);

what I need is to create a object by passing a undetermined number of variables into it’s constructor.

Answer 1

You can do this with Reflection:

<?php

class Pants
{
    public function __construct($a, $b, $c)
    {
        $this->a = $a;
        $this->b = $b;
        $this->c = $c;
    }
}

$className = 'pants';
$class = new ReflectionClass($className);
$obj = $class->newInstanceArgs(array(1, 2, 3));
var_dump($obj);

This will also work if your constructor uses the old style (unless your code makes use of namespaces and you are using PHP 5.3.3 or, presumably, greater, as old-style constructors will no longer work with namespaced code – more info):

<?php
class Pants {
    function Pants($a, $b, $c) { ... }
}

If the class has no constructor and you wish to use reflection, use $class->newInstance() instead of $class->newInstanceArgs(...). To do this dynamically, it would look like this:

$object = null === $class->getConstructor() 
    ? $class->newInstance()
    : $class->newInstanceArgs($args)
;