Function handling Functions
Many people have wondered how to effectively implement dispatch tables in PHP. Here's my answer to that (if you'll forgive my creative flair):
<?php
/*
* Using dispatch tables in PHP.
*
* --Kris Craig
*/
define( "YOUR_MOTHER", 1 );
define( "YOUR_FATHER", 2 );
define( "YOUR_BROTHER", 3 );
define( "YOUR_SISTER", 4 );
class MyFamily
{
static $dispatch = array( YOUR_MOTHER => "Mom", YOUR_FATHER => "GetPrisonInmate", YOUR_BROTHER => "ReplaceName", YOUR_SISTER => "LazyGirl" );
static $args = array( YOUR_MOTHER => array(), YOUR_FATHER => array( "55170-054", TRUE ), YOUR_BROTHER => array(), YOUR_SISTER => array() );
function GetDispatch( $fromwhere )
{
return call_user_func_array( array( self, self::$dispatch[$fromwhere] ), self::$args[$fromwhere] );
}
function Mom()
{
return "Mommy loves you!";
}
function GetPrisonInmate( $PrisonerID, $GoodBehavior )
{
//Check prison records for his ID, then....
if ( $GoodBehavior )
{
$parole = "APPROVED";
}
else
{
$parole = "DENIED";
}
return "Your father (#$PrisonerID) has $remaining years left in his sentence. His most recent parole application has been: $parole";
}
function ReplaceName()
{
return "Her name is Sally now.";
}
function LazyGirl()
{
print "Your sister needs to get out more....";
//sleep( pow( 60, 2 ) * 18 ); //You can sleep later!
die( "Nah, I'm too tired." );
}
}
print "Status on family member: " . MyFamily::GetDispatch( YOUR_FATHER );
?>
call_user_func_array
(PHP 4 >= 4.0.4, PHP 5)
call_user_func_array — Call a user function given with an array of parameters
Description
Call a user defined function with the parameters in param_arr.
Parameters
- function
-
The function to be called.
- param_arr
-
The parameters to be passed to the function, as an indexed array.
Return Values
Returns the function result, or FALSE on error.
Examples
Example #1 call_user_func_array() example
<?php
function foobar($arg, $arg2) {
echo __FUNCTION__, " got $arg and $arg2\n";
}
class foo {
function bar($arg, $arg2) {
echo __METHOD__, " got $arg and $arg2\n";
}
}
// Call the foobar() function with 2 arguments
call_user_func_array("foobar", array("one", "two"));
// Call the $foo->bar() method with 2 arguments
$foo = new foo;
call_user_func_array(array($foo, "bar"), array("three", "four"));
?>
The above example will output something similar to:
foobar got one and two foo::bar got three and four
Example #2 call_user_func_array() using namespace name
<?php
namespace Foobar;
class Foo {
static public function test($name) {
print "Hello {$name}!\n";
}
}
// As of PHP 5.3.0
call_user_func_array(__NAMESPACE__ .'\Foo::test', array('Hannes'));
// As of PHP 5.3.0
call_user_func_array(array(__NAMESPACE__ .'\Foo', 'test'), array('Philip'));
?>
The above example will output something similar to:
Hello Hannes! Hello Philip!
Example #3 Using lambda function
<?php
$func = function($arg1, $arg2) {
return $arg1 * $arg2;
};
var_dump(call_user_func_array($func, array(2, 4))); /* As of PHP 5.3.0 */
?>
The above example will output:
int(8)
Notes
Note:
Referenced variables in param_arr are passed to the function by a reference, others are passed by a value. In other words, it does not depend on the function signature whether the parameter is passed by a value or by a reference.
Note:
Callbacks registered with functions such as call_user_func() and call_user_func_array() will not be called if there is an uncaught exception thrown in a previous callback.
See Also
- call_user_func() - Call a user function given by the first parameter
- information about the callback type
add a note
User Contributed Notescall_user_func_array
Kris dot Craig at gmail dot com
16-Jun-2010 04:28
16-Jun-2010 04:28
noone at example dot com
21-Apr-2010 04:03
21-Apr-2010 04:03
For those of you that have to consider performance: it takes about 3 times as long to call the function this way than via a straight statement, so whenever it is feasible to avoid this method it's a wise idea to do so.
Note that eval() is about 10 times slower than a straight statement to call a function with arguments, so this is definitely a better option than using eval() even if you only consider performance.
Guy Paddock
15-Apr-2010 03:14
15-Apr-2010 03:14
It appears that it is safe to pass an associative array in for $param_arr. The parameters will still be passed in the order the elements appear in the array, not alphabetical key order.
kweejee at gmail dot com
22-Jan-2010 09:04
22-Jan-2010 09:04
I recently had
<?php
call_user_func_array('MyClass::myFunction', array(0, 10));
?>
working on my home server, but when I uploaded it to a host with a different version of PHP it stopped working and gave the error message "call_user_func_array() [function.call-user-func-array]: Unable to call MyClass::myFunction()" The solution I found was to use this instead:
<?php
call_user_func_array(array('MyClass', 'myFunction'), array(0, 10));
?>
aj at ajbrown dot org
22-Dec-2009 08:30
22-Dec-2009 08:30
Just a heads up, the second parameter MUST be an array if it's specified, but that doesn't seem to be enforced until ~5.3.
I just pulled my hair out with an old installation of CakePHP because it was passing NULL instead of an empty array.
mrextreme at freemail dot hu
07-Dec-2009 09:34
07-Dec-2009 09:34
If you are using PHP < 5.3 and want to call the parent class' __construct() with a variable parameter list, use this:
<?php
public function __construct()
{
$vArgs = func_get_args(); // you can't just put func_get_args() into a function as a parameter
call_user_func_array(array('parent', '__construct'), $vArgs);
}
?>
dmitry dot revenko at businessmedia dot ru
25-Sep-2009 06:28
25-Sep-2009 06:28
Just hope this note helps someone (I killed the whole day on issue).
If you use something like this in PHP < 5.3:
<?php call_user_func_array(array($this, 'parent::func'), $args); ?>
Such a script will cause segmentation fault in your webserver.
In 5.3 you should write it:
<?php call_user_func_array('parent::func', $args); ?>
al dot james at NOSPAMGMAIL dot com
17-Jun-2009 04:19
17-Jun-2009 04:19
If you want to use call_user_func_array to call an objects constructor, this works for me:
<?php
$obj = new $object_class();
call_user_func_array(array($obj, '__construct'), $args);
?>
(However it does depend on having a constructor where all arguments are optional, which may or may not be possible)
So this is a two part initiation, the object gets initiated with no arguments first (hence requiring options constructor params), and then __construct gets called again. Thus, you should not do anything in your constructor that triggers effects outside the class... it should just set the objects state.
Damin
13-Jun-2009 01:06
13-Jun-2009 01:06
Those having the passing by reference issue can use this simple hack.
I´m really not sure WHY this works, but it does, and it does not make use of EVAL or other questionable functions.
<?php
function executeHook($name, $type='hooks'){
$args = func_get_args();
array_shift($args);
array_shift($args);
//Rather stupid Hack for the call_user_func_array();
$Args = array();
foreach($args as $k => &$arg){
$Args[$k] = &$arg;
}
//End Hack
$hooks = &$this->$type;
if(!isset($hooks[$name])) return false;
$hook = $hooks[$name];
call_user_func_array($hook, $Args);
}
?>
All it´s doing is copying the args ($args) into a new array ($Args) by reference, which i would think would be identical to the original array in every way (that matters).
Note the code here is an example of usage. The actual hack is denoted by comments.
If someone knows a better alternative, by all means, i would love to see it.
Freek (at) Gruntjes.net
07-Apr-2009 02:53
07-Apr-2009 02:53
I just noticed that when you use this function with parameters that need to be passed by reference it will not work.
<?php
function refFunc(&$var)
{
$var .= 'bar';
}
$var = 'foo';
?>
call_user_func_array('refFunc', array($var));
echo $var;
will output 'foo' and not 'foobar'. Witch is logical since you are declaring a new variable with array($var) however not so obvious.
thiago dot henrique dot mata at gmail dot com
22-Jul-2008 03:17
22-Jul-2008 03:17
<?php
Class Delegate
{
private $arrInstances = array();
protected function addObject( $oElement )
{
// add one element on the end of the stack //
$this->arrInstances[] = $oElement;
}
public function __call( $strMethod, $arrParams )
{
// for each element in instance //
foreach( $this->arrInstances as $oElement )
{
// get the class of the element //
$strClass = get_class( $oElement );
// get all methods of the class //
$arrMethods = get_class_methods( $strClass );
// case the method exists into this class //
if( in_array( $strMethod , $arrMethods ) )
{
// prepare caller //
$arrCaller = Array( $strClass , $strMethod );
// return the result of the method into the object //
return call_user_func_array( $arrCaller, $arrParams );
}
}
// any object has the method //
// throw a exception //
throw new Exception( " Method " . $strMethod . " not exist in this class " . get_class( $this ) . "." );
}
}
class Log
{
public function sayHi()
{
print "hi!" . "<br/>\n";
}
public function sayMyName()
{
print "log" . "<br/>\n";
}
}
class Other
{
public function sayHello()
{
print "hello there!" . "<br/>\n";
}
public function sayMyName()
{
print "other" . "<br/>\n";
}
}
class Example extends Delegate
{
public function __construct()
{
$this->addObject( new Log() );
$this->addObject( new Other() );
}
}
$oExample = new Example();
$oExample->sayHi();
$oExample->sayHello();
$oExample->sayMyName();
/*
hi!<br/>
hello there!<br/>
log<br/>
*/
?>
dnhuff at acm.org
07-Jun-2008 12:57
07-Jun-2008 12:57
It appears that when PHP executes something like:
$a = array(1,2,3);
$b =& $a[1];
both $b and $a[1] are converted into references to a common value -- makes sense until you transfer that to a call_user_func:
call_user_func_array('foo', $a);
suddenly, inside foo, the second parameter is passed by reference!
And you can't call this wrong, only another subtly of references.
Note it appears that ksort($a) will remove the reference as well as put the elements in key order so you (probably) get what you expect. (see below on the use of a foreach ($a as &v).)
dnhuff at acm.org
07-Jun-2008 12:38
07-Jun-2008 12:38
the order of argument correspondence from the array to the function formal parameters is by 'natural order' of the array and not explicit numerical key order.
So: $a[0] = 'arg 1'; $a[2] = 'arg 2'; $a[1] = 'arg 3';
call_user_func_array('foo', $a);
delivers the args to foo in the order the keys were inserted! as in...
foo($a[0], $a[2], $a[1]);
if you wanted something else, ksort the array first.
aeolianmeson at 8n54tvv dot blitzeclipse dot com
27-May-2008 09:48
27-May-2008 09:48
There's a possibility that call_user_func_array(), call_user_func(), and Exception::getTrace() will cause a trace entry to not have the 'file' or 'line' elements.
Dustin Oprea
richard_harrison at rjharrison dot org
11-Apr-2007 03:31
11-Apr-2007 03:31
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 03:50
08-Feb-2007 03:50
Regarding the comments below about calling parent constructors:
PHP5 with E_STRICT no longer allows calls as below:
<?php
// Causes an error with E_STRICT
call_user_func_array(array('parent', '__construct'), $args);
?>
It gives an error because you are trying to call a nonstatic function as if it was static. The correct syntax is
<?php
// Works fine
call_user_func_array(array($this, 'parent::__construct'), $args);
?>
15-May-2006 03:43
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, $real_params);
}
?>
eugene at artprime dot ru
23-Dec-2005 03:59
23-Dec-2005 03:59
<?php
return call_user_func_array(
array(new ReflectionClass($className), 'newInstance'),
$functionParameters
);
?>
Look here: http://www.zend.com/zend/week/week182.php#Heading1
crocodile2u at yandex dot ru
20-Dec-2005 06:06
20-Dec-2005 06:06
Here is another version of createObjArray() function written here earlier by taylor.
Believing that using 'eval()' is at least "dirty", I came to the following solution (with a help of panchous - at phpclub dot ru forums ). This solution utilizes the new Reflection API.
<?php
function & createObjArray($type, $args = array()) {
$reflection = new ReflectionClass($type);
$output = call_user_func_array(array(&$reflection, 'newInstance'), $args);
return $output;
}
?>
Egor
15-Nov-2005 10:35
15-Nov-2005 10:35
Note that, despite the name, this does work on builtin functions (and object methods with the array(&$obj, $method) syntax), not just user-defined functions and methods.
rrant (at) gmail (dot) com
10-Nov-2005 04:50
10-Nov-2005 04:50
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'), $args);
// ... Your Code Here ...
}
?>
Note that your constructor pass all the arguments to the parent constructor and it doesn't matter how many arguments you pass.
This is pretty useful for constructors with a variable number of arguments.
taylor
02-Jun-2005 06:51
02-Jun-2005 06:51
I came up with a better solution to the problem that I solve below with createObjArray that maintains parameter type:
<?php
function createObjArray($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 04:04
07-May-2005 04:04
<?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($seval);
}
?>
amer at o2 dot pl
20-Jan-2005 03:44
20-Jan-2005 03:44
PLS notice that "patripaq at hotmail dot com" 's code will be valid if B EXTENDS A...
<?php
class B extends A{
...
}
?>
there>>"What I wanted to do is create an object that can manage any number and any kind of parameters."
BUT IT IS NOT A POINT AT ALL
If you need to call just function with parameters:
call_user_func_array('Foo',$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'), $args );
}
}
?>
Then there can be any number and any type of created object B parameters
james at gogo dot co dot nz
21-Nov-2004 06:19
21-Nov-2004 06:19
Be aware the call_user_func_array always returns by value, as demonstrated here...
<?php
function &foo(&$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 06:31
25-Oct-2004 06:31
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 04:49
06-Aug-2004 04:49
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...
}
}
$obj = new B( 'param1', 'param2' );
//--------------------------
?>
hong dot nguyen at k-edge dot com
02-Apr-2004 10:37
02-Apr-2004 10:37
call_user_func_array can pass parameters as reference:
<?php
call_user_func_array(array(&$obj,$method),array(&$arg1,$arg2,$arg3))
?>
Use it as work-around for "Call-time pass-by-reference has been deprecated".
adamh at densi dot com
31-Jul-2003 12:58
31-Jul-2003 12:58
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 $array could have any number of arrays inside it.
gord at fig dot org
06-May-2003 05:30
06-May-2003 05:30
If you need to call object and class methods in PHP < 4.0.4, the following code ought to do the trick:
<?php
if (!function_exists('call_user_func_array')) {
function call_user_func_array($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 01:29
12-Mar-2003 01:29
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 05:19
22-Jun-2002 05:19
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);
?>