PHP 支援變數函式的概念。這表示如果一個變數名稱後面加上括號，PHP 會尋找與該變數值同名的函式，並嘗試執行它。 除其他外，這可以用於實現回調、函式表等等。
變數函式不適用於語言結構，例如 echo、print、unset()、isset()、empty()、include、require 等。 使用包裝函式可以將這些結構作為變數函式使用。
範例 #1 變數函式範例
<?php
function foo() {
echo "In foo()<br />\n";
}
function bar($arg = '')
{
echo "In bar(); argument was '$arg'.<br />\n";
}
// 這是 echo 的一個包裝函式
function echoit($string)
{
echo $string;
}
$func = 'foo';
$func(); // 這會呼叫 foo()
$func = 'bar';
$func('test'); // 這會呼叫 bar()
$func = 'echoit';
$func('test'); // 這會呼叫 echoit()
?>物件方法也可以使用變數函式語法來呼叫。
範例 #2 變數方法範例
<?php
class Foo
{
function Variable()
{
$name = 'Bar';
$this->$name(); // 這會呼叫 Bar() 方法
}
function Bar()
{
echo "This is Bar";
}
}
$foo = new Foo();
$funcname = "Variable";
$foo->$funcname(); // 這會呼叫 $foo->Variable()
?>呼叫靜態方法時，函式呼叫的優先順序高於靜態屬性運算子。
範例 #3 使用靜態屬性的變數方法範例
<?php
class Foo
{
static $variable = 'static property';
static function Variable()
{
echo 'Method Variable called';
}
}
echo Foo::$variable; // 這會印出 'static property'。在這個作用域中不需要 $variable。
$variable = "Variable";
Foo::$variable(); // 這會呼叫 $foo->Variable()，並讀取此作用域中的 $variable。
?>
範例 #4 複雜的可呼叫物件
<?php
class Foo
{
static function bar()
{
echo "bar\n";
}
function baz()
{
echo "baz\n";
}
}
$func = array("Foo", "bar");
$func(); // 顯示 "bar"
$func = array(new Foo, "baz");
$func(); // 顯示 "baz"
$func = "Foo::bar";
$func(); // 顯示 "bar"
?>雖然文件建議常數的用法類似於變數的用法，但在可變函數方面有一個例外。您不能使用常數作為函數名稱來呼叫可變函數。
const DEBUGME ='func';
function func($s) { echo $s. "\n"; }
DEBUGME('abc'); // 導致語法錯誤
$call = DEBUGME;
$call('abc'); // 可以正常運作
但是您可以將常數用作函數的參數。以下是當您需要呼叫可變常數函數時的簡單解決方法
function dynamic($what, $with)
{
$what($with);
}
dynamic(DEBUGME, 'abc');
這對我來說很有意義，可以隱藏 API 和/或冗長（複雜）的靜態呼叫。
享受吧！<?php
/*
You might have found yourself at this php variable functions page because, like me, you wanted to pass functions
around like objects to client objects as you can in JavaScript. The issue I ran into was although
I could call a function using a variable like this " $v(); "...I could not do it like this " $obj->p() " where
'p' is a property containing the name of the method to call. Did not want to save my property off to a variable prior
to making my call: " $v = $obj->p; $v(); "; even if one finds a way, the below applies...
I credit this expanded work to this person: tatarynowicz at gmail dot com;
without them I would not have gotten here.
*/
interface iface_dynamic_members{
//Use of this interface enables type-hinting for objects that implement it.
public function __call($name, $args);
public function __set($name, $value);
public function quietly_fail():bool;
}
trait trait_has_dynamic_members{
//Implementing these magic methods in the form of a trait, frees the client object up
//so it can still inherit from a parent-class.
public function __call($name, $args) {
if (is_callable($this->$name)) {
return call_user_func($this->$name, $args);
}
else {
//Your dynamic-membered object can declare itself as willing to ignore non-existent method calls or not.
if($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; //Assignment using ternary operator.
}
}
abstract class MBR_ATTR{
//A class full of attributes that objects can take on; abstract since not to be instantiated (If I could make it "final" as well, I would).
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); //If can run, also can walk.
}
}
class cls_partly_dynamic implements iface_dynamic_members{
use trait_has_dynamic_members;
public function quietly_fail():bool{
return true;
}
}
// Report all errors except E_NOTICE
error_reporting(E_ALL & ~E_NOTICE); //Enable all error-reporting except notices.
//----
//config runner object...
$obj_runner = new cls_partly_dynamic();
MBR_ATTR::is_a_runner($obj_runner, 'fast');
$obj_runner->runner_type = 'a bit slow';
//----
//config walker object...
$obj_walker = new cls_partly_dynamic();
MBR_ATTR::is_a_walker($obj_walker, 'slow');
$obj_walker->walker_type = 'super fast';
//----
//Do stuff...
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 $obj_runner->xxx() . '<br>'; //Try calling a non-existent method.
//I would agree that the above approach/technique is not always ideal, particulary due to the loss of code-completion in your
//IDE of choice; I would tend to use this approach for dynamic-programming in response to the user dictating processing steps via a UI.
?>$ wget https://php.dev.org.tw/get/php_manual_en.tar.gz/from/a/mirror
$ grep -l "\$\.\.\." php-chunked-xhtml/function.*.html
接受可變參數的函數列表。
<?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()
?>