PHP supports the concept of variable functions. This means that if a variable name has parentheses appended to it, PHP will look for a function with the same name as whatever the variable evaluates to, and will attempt to execute it. Among other things, this can be used to implement callbacks, function tables, and so forth.
Variable functions won't work with language constructs such as echo, print, unset(), isset(), empty(), include, require and the like. Utilize wrapper functions to make use of any of these constructs as variable functions.
Example #1 Variable function example
<?php
function foo() {
echo "In foo()<br />\n";
}
function
bar($arg = '')
{
echo "In bar(); argument was '$arg'.<br />\n";
}// This is a wrapper function around echo
function echoit($string)
{
echo $string;
}$func = 'foo';
$func(); // This calls foo()$func = 'bar';
$func('test'); // This calls bar()$func = 'echoit';
$func('test'); // This calls echoit()
?>
Object methods can also be called with the variable functions syntax.
Example #2 Variable method example
<?php
class Foo
{
function Variable()
{
$name = 'Bar';
$this->$name(); // This calls the Bar() method
}
function
Bar()
{
echo "This is Bar";
}
}$foo = new Foo();
$funcname = "Variable";
$foo->$funcname(); // This calls $foo->Variable()?>
When calling static methods, the function call is stronger than the static property operator:
Example #3 Variable method example with static properties
<?php
class Foo
{
static $variable = 'static property';
static function Variable()
{
echo 'Method Variable called';
}
}
echo
Foo::$variable; // This prints 'static property'. It does need a $variable in this scope.
$variable = "Variable";
Foo::$variable(); // This calls $foo->Variable() reading $variable in this scope.?>
Example #4 Complex callables
<?php
class Foo
{
static function bar()
{
echo "bar\n";
}
function baz()
{
echo "baz\n";
}
}$func = array("Foo", "bar");
$func(); // prints "bar"
$func = array(new Foo, "baz");
$func(); // prints "baz"
$func = "Foo::bar";
$func(); // prints "bar"
?> niemans at pbsolo dot nl ¶
6 years ago
While the documentation suggests that the use of a constant is similar to the use of a variable, there is an exception regarding variable functions. You cannot use a constant as the function name to call a variable function.
const DEBUGME ='func';
function func($s) { echo $s. "\n"; }
DEBUGME('abc'); // results in a syntax error
$call = DEBUGME;
$call('abc'); // does the job
But you can use a constant as an argument to a function. Here's a simple workaround when you need to call a variable constant function:
function dynamic($what, $with)
{
$what($with);
}
dynamic(DEBUGME, 'abc');
This makes sense to me to hide API's and/or long (complicated) static calls.
Enjoy! rnealxp at yahoo dot com ¶
4 years ago
<?php
interface iface_dynamic_members{
public function __call($name, $args);
public function __set($name, $value);
public function quietly_fail():bool;
}
trait trait_has_dynamic_members{
public function __call($name, $args) {
if (is_callable($this->$name)) {
return call_user_func($this->$name, $args);
}
else {
if($this->quietly_fail()===true){
echo 'Method does not exist, but I do not mind.';
}else{
echo 'Method does not exist, I consider this a bug.';
}
}
}
public function __set($name, $value) {
$this->$name = is_callable($value) ? $value->bindTo($this, $this): $value; }
}
abstract class MBR_ATTR{
public static function is_a_walker(iface_dynamic_members $obj, ?string $walker_type='normal pace'){
$obj->walker_type = $walker_type;
$obj->walker_walk = function() {
return "I am walking {$this->walker_type}.";
};
}
public static function is_a_runner(iface_dynamic_members $obj, string $runner_type){
$obj->runner_type = $runner_type;
$obj->runner_run = function() {
return "I am running {$this->runner_type}.";
};
self::is_a_walker($obj); }
}
class cls_partly_dynamic implements iface_dynamic_members{
use trait_has_dynamic_members;
public function quietly_fail():bool{
return true;
}
}
error_reporting(E_ALL & ~E_NOTICE); $obj_runner = new cls_partly_dynamic();
MBR_ATTR::is_a_runner($obj_runner, 'fast');
$obj_runner->runner_type = 'a bit slow';
$obj_walker = new cls_partly_dynamic();
MBR_ATTR::is_a_walker($obj_walker, 'slow');
$obj_walker->walker_type = 'super fast';
echo 'walker in action...' . '<br>';
echo $obj_walker->walker_walk() . '<br>';
echo '<br>';
echo 'runner in action...' . '<br>';
echo $obj_runner->walker_walk() . '<br>';
echo $obj_runner->runner_run() . '<br>';
echo $obj_runner->xxx() . '<br>'; ?> Anonymous ¶
13 years ago
$ wget http://www.php.net/get/php_manual_en.tar.gz/from/a/mirror
$ grep -l "\$\.\.\." php-chunked-xhtml/function.*.html
List of functions that accept variable arguments.
<?php
array_diff_assoc()
array_diff_key()
array_diff_uassoc()
array()
array_intersect_ukey()
array_map()
array_merge()
array_merge_recursive()
array_multisort()
array_push()
array_replace()
array_replace_recursive()
array_unshift()
call_user_func()
call_user_method()
compact()
dba_open()
dba_popen()
echo()
forward_static_call()
fprintf()
fscanf()
httprequestpool_construct()
ibase_execute()
ibase_set_event_handler()
ibase_wait_event()
isset()
list()
maxdb_stmt_bind_param()
maxdb_stmt_bind_result()
mb_convert_variables()
newt_checkbox_tree_add_item()
newt_grid_h_close_stacked()
newt_grid_h_stacked()
newt_grid_v_close_stacked()
newt_grid_v_stacked()
newt_win_choice()
newt_win_entries()
newt_win_menu()
newt_win_message()
newt_win_ternary()
pack()
printf()
register_shutdown_function()
register_tick_function()
session_register()
setlocale()
sprintf()
sscanf()
unset()
var_dump()
w32api_deftype()
w32api_init_dtype()
w32api_invoke_function()
wddx_add_vars()
wddx_serialize_vars()
?>
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