Question

How can I create a class with a given array of arguments to be sent to the constructor? Something along the lines of:

class a {
    var $args = false;
    function a() {$this->args = func_get_args();}
}

$a = call_user_func_array('new a',array(1,2,3));
print_r($a->args);

Ideally this needs to work, without modification to the class, in both PHP4 and PHP5. Any ideas?

Answer 1

ReflectionClass:newInstance() (or newInstanceArgs()) let’s you do that.

e.g.

class Foo {
  public function __construct() {  
    $p = func_get_args();
    echo 'Foo::__construct(', join(',', $p), ') invoked';
  }
}

$rc = new ReflectionClass('Foo');
$foo = $rc->newInstanceArgs( array(1,2,3,4,5) );

edit: without ReflectionClass and probably php4 compatible (sorry, no php4 at hand right now)

class Foo {
  public function __construct() {  
    $p = func_get_args();
    echo 'Foo::__construct(', join(',', $p), ') invoked';
  }
}

$class = 'Foo';
$rc = new $class(1,2,3,4);

speed comparison:
Since the speed of reflection has been mentioned here’s a little (synthetic) test

define('ITERATIONS', 100000);

class Foo {
  protected $something;
  public function __construct() {
    $p = func_get_args();
    $this->something = 'Foo::__construct('.join(',', $p).')';
  }
}

$rcStatic=new ReflectionClass('Foo'); 
$fns = array(
  'direct new'=>function() { $obj = new Foo(1,2,3,4); },
  'indirect new'=>function() { $class='Foo'; $obj = new $class(1,2,3,4); }, 
  'reflection'=>function() { $rc=new ReflectionClass('Foo'); $obj = $rc->newInstanceArgs( array(1,2,3,4) ); },
  'reflection cached'=>function() use ($rcStatic) { $obj = $rcStatic->newInstanceArgs( array(1,2,3,4) ); },
);


sleep(1);
foreach($fns as $name=>$f) {
  $start = microtime(true);
  for($i=0; $i<ITERATIONS; $i++) {
    $f();
  }
  $end = microtime(true);
  echo $name, ': ', $end-$start, "\n";
  sleep(1);
}

which prints on my (not so fast) notebook

direct new: 0.71329689025879
indirect new: 0.75944685935974
reflection: 1.3510940074921
reflection cached: 1.0181720256805

Isn’t that bad, is it?