Instantiating a new PHP class with one or many arguments

Question

I have this fetch function:

public static function fetch($class, $key)
{
    try
    {
        $obj = new $class($key);
    }
    catch(Exception $e)
    {
        return false;
    }
    return $obj;
}

It creates a new instance by calling that class's constructor and passing in the key. Now, how would I make it so I can pass in an array of arguments in $key, and have it like:

$obj = new $class($key[0], $key[1]...);

So that it works for one or more keys?

Hopefully that was clear enough.

Using PHP 5

Answer 1

What does the constructor of the class look like? Does it accept an arbitrary number of arguments? It might be better to accept an array of keys instead of a list of key arguments.

call_user_func_array could probably do what you want:

$obj = new $object_class();
call_user_func_array(array($obj, '__construct'), $args);

Note that this calls the constructor twice, which could have negative side effects.

Answer 2

Use reflection:

$classReflection = new ReflectionClass($class);
$obj = $classReflection->newInstanceArgs($key);

Answer 3

My library solves this this:

// Returns a new instance of a `$classNameOrObj`.
function fuNew($classNameOrObj, $constructionParams = array()) {
    $class = new ReflectionClass($classNameOrObj);
    if (empty($constructionParams)) { return $class->newInstance(); }
    return $class->newInstanceArgs($constructionParams); }

The empty() test is required because newInstanceArgs() will complain if you give it an empty array, stupidly.

Answer 4

This is an interesting question. If it wasn't a constructor function you were trying to give dynamic arguments to, then normally you could use call_user_func_array(). However, since the new operator is involved, there doesn't seem to be an elegant way to do this.

Reflection seems to be the consensus from what I could find. The following snippet is taken from the user comments on call_user_func_array(), and illustrates the usage quite nicely:

<?php

// arguments you wish to pass to constructor of new object
$args = array('a', 'b');

// class name of new object
$className = 'myCommand';

// make a reflection object
$reflectionObj = new ReflectionClass($className);

// use Reflection to create a new instance, using the $args
$command = $reflectionObj->newInstanceArgs($args);

// this is the same as: new myCommand('a', 'b');
?>

To shorten it up for your case, you can use:

$reflectionObject = new ReflectionClass($class);
$obj = $reflectionObject->newInstanceArgs($key);