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call_user_func_array

Sc00bz
05-Sep-2007 12:11


After looking at "php at paulbutler dot org" comment I tested the hack with a pass by value function just because I thought it might do something wrong, well it did.



<?php

function setargs($a1, $a2, $a3) // all are pass by value

{

    $a1 = "one";

    $a2 = "two";

    $a3 = "three";

}



$args = array("1","2","3");



$hack = array();

foreach ($args as &$v)

    $hack[] =& $v;



call_user_func_array("setargs", $args);

echo implode(" ", $args);

?>



Displays "one two three", instead of the expected "1 2 3".

Someone should really test this on the current version of php and report this bug.

php at paulbutler dot org
31-Jul-2007 03:13


There is weird behavior on this function in terms of passing variables by reference. It seems that despite what the manual says, if a reference to the variable exists it will be passed by reference.



For instance, take the following code:



<?php

function setargs(&$a1, &$a2, &$a3){

    $a1 = "one";

    $a2 = "two";

    $a3 = "three";

}



$args = array('1','2','3');

call_user_func_array('setargs', $args);

echo implode(' ', $args);

?>



The above code will display "1 2 3", indicating that the variables were passed by value.



However, take the following code:



<?php



function setargs(&$a1, &$a2, &$a3){

    $a1 = "one";

    $a2 = "two";

    $a3 = "three";

}



$args = array('1','2','3');



$hack = array();

for($i = 0; $i < count($args); $i++){

    $hack[] =& $args[$i];

}



call_user_func_array('setargs', $args);

echo implode(' ', $args);



?>



Which displays "one two three", instead of the expected "1 2 3".



This appears to be a bug in PHP, but it is a useful one because it makes it possible to pass variables by reference to a user function call. Of course it is dangerous to rely on a hack, especially one that only works because of a bug, but if you know what you are doing this could help you get around this limitation of call_user_func_array.

richard_harrison at rjharrison dot org
11-Apr-2007 02:31


If you are thinking of using call_user_func_array to instantiate an object (see comments below using Reflection) then since v5.1.3 you can use the Reflection::newInstanceArgs() method.



<?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');

?>

levi at alliancesoftware dot com dot au
08-Feb-2007 02:50


Regarding the comments below about calling parent constructors:



PHP5 with E_STRICT no longer allows calls as below:

<?

// Causes an error with E_STRICT

call_user_func_array(array('parent', '__construct'), $args);

?>



It gives an error because you are trying to call a nonstatic function as if it was static. The correct syntax is



<?

// Works fine

call_user_func_array(array($this, 'parent::__construct'), $args);

?>

15-May-2006 02:43


For those wishing to implement call-by-name functionality in PHP, such as implemented e.g. in DB apis, here's a quick-n-dirty version for PHP 5 and up

<?php

/**

 * Call a user function using named instead of positional parameters.

 * If some of the named parameters are not present in the original function, they

 * will be silently discarded.

 * Does no special processing for call-by-ref functions...

 * @param string $function name of function to be called

 * @param array $params array containing parameters to be passed to the function using their name (ie array key)

 */

function call_user_func_named($function, $params)

{

    // make sure we do not throw exception if function not found: raise error instead...

    // (oh boy, we do like php 4 better than 5, don't we...)

    if (!function_exists($function))

    {

        trigger_error('call to unexisting function '.$function, E_USER_ERROR);

        return NULL;

    }

    $reflect = new ReflectionFunction($function);

    $real_params = array();

    foreach ($reflect->getParameters() as $i => $param)

    {

        $pname = $param->getName();

        if ($param->isPassedByReference())

        {

            /// @todo shall we raise some warning?

        }

        if (array_key_exists($pname, $params))

        {

            $real_params[] = $params[$pname];

        }

        else if ($param->isDefaultValueAvailable()) {

            $real_params[] = $param->getDefaultValue();

        }

        else

        {

            // missing required parameter: mark an error and exit

            //return new Exception('call to '.$function.' missing parameter nr. '.$i+1);

            trigger_error(sprintf('call to %s missing parameter nr. %d', $function, $i+1), E_USER_ERROR);

            return NULL;

        }

    }

    return call_user_func_array($function, $real_params);

}

?>

eugene at artprime dot ru
23-Dec-2005 02:59


<?php

  return call_user_func_array(

    array(new ReflectionClass($className), 'newInstance'),

    $functionParameters

  );

?>



Look here: http://www.zend.com/zend/week/week182.php#Heading1

crocodile2u at yandex dot ru
20-Dec-2005 05:06


Here is another version of createObjArray() function written here earlier by taylor.



Believing that using 'eval()' is at least "dirty", I came to the following solution (with a help of panchous - at phpclub dot ru forums ). This solution utilizes the new Reflection API.



<?php

function & createObjArray($type, $args = array()) {

    $reflection = new ReflectionClass($type);

    $output     = call_user_func_array(array(&$reflection, 'newInstance'), $args);

    return $output;

}

?>

Egor
15-Nov-2005 09:35


Note that, despite the name, this does work on builtin functions (and object methods with the array(&$obj, $method) syntax), not just user-defined functions and methods.

rrant (at) gmail (dot) com
10-Nov-2005 03:50


Just an extra for the post of amer at o2 dot pl:



If you need to call the PARENT method:

call_user_func_array(array('parent', 'method'), $args);



With that, if you need to call a constructor and/or add some extra code to the instantiation process:



<?php

function __construct() {

    // Get the arguments

    $args = func_get_args();

    // Initialize parent with arguments

    call_user_func_array(array('parent', '__construct'), $args);

    // ... Your Code Here ...

}

?>



Note that your constructor pass all the arguments to the parent constructor and it doesn't matter how many arguments you pass.



This is pretty useful for constructors with a variable number of arguments.

taylor
02-Jun-2005 05:51


I came up with a better solution to the problem that I solve below with createObjArray that maintains parameter type:



<?php



function createObjArray($type,$args=array()) {

     $paramstr = '';

     for ($i = 0; $i < count($args); $i++) {

           $paramstr .= '$args['.$i.'],';

     }

     $paramstr = rtrim($paramstr,',');



     return eval("return new $type($paramstr);");

}



?>



Would be good to add error checking, but it works.

taylor
07-May-2005 03:04


<?php

    /**

     * Create an object of a specified type using an array as the parameters

     * to the constructor.  NOTE: does not maintain proper 

     * types for the arguments.  They are all converted to strings.

     * @param $type Type type of object to create (class name)

     * @param $args The arguments to pass to the constructor

     */

    function createObjArray($type, $args=array()) {

        if ( !class_exists($type) ) {

            return NULL;

        }

        

        // build argument list; be sure to escape string delimeters

        $func = create_function('$str', 'return str_replace("\'","\\\'",$str);');

        $sargs = "'" . join( "','", array_map($func,$args) ). "'";

        

        // build & eval code; return result

        $seval = "return new $type($sargs);";

        return eval($seval);

    }

?>

amer at o2 dot pl
20-Jan-2005 02:44


PLS notice that "patripaq at hotmail dot com" 's code will be valid if B EXTENDS A...

<?php

class B extends A{

...

} 

?>

there>>"What I wanted to do is create an object that can manage any number and any kind of parameters."



BUT IT IS NOT A POINT AT ALL



If you need to call just function with parameters:

call_user_func_array('Foo',$args);



If you need to call CLASS method (NOT object):

call_user_func_array(array('class', 'Foo'),$args); 



If you need to call OBJECT method:

call_user_func_array(array(&$Object, 'Foo'),$args);



If you need to call method of object of object:

call_user_func_array(array(&$Object->Object, 'Foo'),$args);



If you need to call object method from within the very same object (NOT CLASS!):

call_user_func_array(array(&$this, 'Foo'),args);



The call_user_func_array ITSELF can manage any number and any kind of parameters. It can handle ANY FUNCTION too as it is defined and that maybe partipaq wanted to manage. 



What You actually need is object composition not inheritance. Make an instance from arguments. 

<?php

...

class B{

   function __construct() {

      $args = func_get_args(); // Get arguments

      $this->OBJ = new A($args);

      call_user_func_array(array(&$this->OBJ, 'A'), $args );

   }

}

?>

Then there can be any number and any type of created object B parameters

james at gogo dot co dot nz
21-Nov-2004 05:19


Be aware the call_user_func_array always returns by value, as demonstrated here...



<?php    

    function &foo(&$a)

    {

      return $a;

    }

    

    $b = 2;

    $c =& call_user_func_array('foo', array(&$b));

    $c++;

    echo $b . ' ' . $c;    

?>



outputs "2 3", rather than the expected "3 3".



Here is a function you can use in place of call_user_func_array which returns a reference to the result of the function call. 



<?php

    function &ref_call_user_func_array($callable, $args)

    {

        if(is_scalar($callable))

        {

            // $callable is the name of a function

            $call = $callable;

        }

        else

        {

            if(is_object($callable[0]))

            {

                // $callable is an object and a method name

                $call = "\$callable[0]->{$callable[1]}";

            }

            else

            {

                // $callable is a class name and a static method

                $call = "{$callable[0]}::{$callable[1]}";

            }

        }

        

        // Note because the keys in $args might be strings

        // we do this in a slightly round about way.

        $argumentString = array();

        $argumentKeys = array_keys($args);

        foreach($argumentKeys as $argK)

        {

            $argumentString[] = "\$args[$argumentKeys[$argK]]";

        }

        $argumentString = implode($argumentString, ', ');

        // Note also that eval doesn't return references, so we 

        // work around it in this way...    

        eval("\$result =& {$call}({$argumentString});");

        return $result;

    }

?>

php at pjt33 dot f2g dot net
25-Oct-2004 05:31


Note that, although it doesn't say so here or in the linked page with information about the callback type, the changelog ( http://www.php.net/ChangeLog-4.php#4.0.5 ) states that call_user_func_array in PHP 4.0.4 won't take an array as the first argument. This was added in 4.0.5.

patripaq at hotmail dot com
06-Aug-2004 03:49


I just started using PHP 5.0 and, so far, I'm loving it !  However, I had a problem the other day and thought it would be a good idea to inform other programmers about the solution I found to get around it.  It concerns the new __constructor() function and the call_user_func_array() function.  What I wanted to do is create an object that can manage any number and any kind of parameters.  Here's the problematic code:



<?php

//--------------------------

class A {

  function __construct() {

    $args = func_get_args(); // Get arguments

    // Class initialization...

  }

  function A() {

    $args = func_get_args(); // Get arguments

    call_user_func_array( array(&$this, '__construct'), $args ); // Infinite loop to B::__construct()...

  }

}



class B {

  function __construct() {

    $args = func_get_args(); // Get arguments

    call_user_func_array( array(&$this, 'A'), $args ); // Initialize parent with arguments

    // Class initialization...

  }

}



$obj = new B( 'param1', 'param2' );

//--------------------------

?>



I suppose you can guess where the problem is located... In the A::A() function, the call to __construct() using call_user_func_array() is redirected to B::__construct() instead of A::__construct().  The only way I found to specify which constructor function I wanted to call was to stop using A::__construct() and use the old fashion constructor instead.  If anyone can find a better way, feel free to add comments.  Here's my solution.  Hope it helps anyone.



<?php

//--------------------------

class A {

  function A() {

    $args = func_get_args(); // Get arguments

    // Class initialization...

  }

}



class B {

  function __construct() {

    $args = func_get_args(); // Get arguments

    call_user_func_array( array(&$this, 'A'), $args ); // Initialize parent with arguments

    // Class initialization...

  }

}



$obj = new B( 'param1', 'param2' );

//--------------------------

?>

hong dot nguyen at k-edge dot com
02-Apr-2004 09:37


call_user_func_array can pass parameters as reference:



<?php

call_user_func_array(array(&$obj,$method),array(&$arg1,$arg2,$arg3))

?>



Use it as work-around for "Call-time pass-by-reference has been deprecated".

mightye (at) mightye (dot) org
12-Mar-2004 09:19


From what I can tell, call_user_func_array *always* passes by value, even if the function asks for a reference (perhaps it duplicates the args before passing them?).

adamh at densi dot com
31-Jul-2003 11:58


call_user_func_array() is nifty for calling PHP functions which use variable argument length. For example:



<?php

$array = array(

 array("foo", "bar"),

 array("bat", "rat"),

);



$values = call_user_func_array("array_merge", $array);



var_dump($values);

?>



/* output:

array(4) {

  [0]=>

  string(3) "foo"

  [1]=>

  string(3) "bar"

  [2]=>

  string(3) "bat"

  [3]=>

  string(3) "rat"

}

*/



The neat feature is that $array could have any number of arrays inside it.

gord at fig dot org
06-May-2003 04:30


If you need to call object and class methods in PHP < 4.0.4, the following code ought to do the trick:



<?php

if (!function_exists('call_user_func_array')) {

    function call_user_func_array($func, $args)

    {

        $argString = '';

        $comma = '';

        for ($i = 0; $i < count($args); $i ++) {

            $argString .= $comma . "\$args[$i]";

            $comma = ', ';

        }



        if (is_array($func)) {

            $obj =& $func[0];

            $meth = $func[1];

            if (is_string($func[0])) {

                eval("\$retval = $obj::\$meth($argString);");

            } else {

                eval("\$retval = \$obj->\$meth($argString);");

            }

        } else {

            eval("\$retval = \$func($argString);");

        }

        return $retval;

    }

}

?>

nutbar at innocent dot com
12-Mar-2003 12:29


This function, combined with some others, can allow you to make some really easy & generic function macros (since real macros don't exist in PHP yet).



<?php

function my_printf() {

   $args = func_get_args();

   return call_user_func_array('printf', $args);

}

?>



This allows you to use my_printf() just as if it were printf() itself.  Very useful since you don't have to worry about how many arguments any functions take.

NOSPAM dot dont dot remove at thekid dot de
22-Jun-2002 04:19


Unified constructors in PHP4:



<?php

  class Object {

    function Object() {

      $args= func_get_args();

      call_user_func_array(array(&$this, '__construct'), $args);

    }



    function __construct($args= NULL) {

      var_dump($args);

    }

  }



  class Exception extends Object {

    var

      $message;

      

    function __construct($message) {

      $this->message= $message;

      parent::__construct();

    }

  }



  class IOException extends Exception {

  }

  

  var_dump(

    error_reporting(), 

    zend_version(), 

    phpversion()

  );

  

  $c= new IOException('file not found');

  

  echo '===> Result: '; var_dump($c);

?>

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