Php using functions with variables
PHP поддерживает концепцию переменных функций. Это означает, что если к имени переменной присоединены круглые скобки, PHP ищет функцию с тем же именем, что и результат вычисления переменной, и пытается её выполнить. Эту возможность можно использовать для реализации обратных вызовов, таблиц функций и множества других вещей.
Переменные функции не будут работать с такими языковыми конструкциями как echo , print , unset() , isset() , empty() , include , require и т.п. Вам необходимо реализовать свою функцию-обёртку для того, чтобы приведённые выше конструкции могли работать с переменными функциями.
Пример #1 Работа с функциями посредством переменных
function bar ( $arg = » )
echo «В bar(); аргумент был ‘ $arg ‘.
\n» ;
>
// Функция-обёртка для echo
function echoit ( $string )
echo $string ;
>
$func = ‘foo’ ;
$func (); // Вызывает функцию foo()
$func = ‘bar’ ;
$func ( ‘test’ ); // Вызывает функцию bar()
$func = ‘echoit’ ;
$func ( ‘test’ ); // Вызывает функцию echoit()
?>
Вы также можете вызвать методы объекта используя возможности PHP для работы с переменными функциями.
Пример #2 Обращение к методам класса посредством переменных
class Foo
function Variable ()
$name = ‘Bar’ ;
$this -> $name (); // Вызываем метод Bar()
>
$foo = new Foo ();
$funcname = «Variable» ;
$foo -> $funcname (); // Обращаемся к $foo->Variable()
При вызове статических методов вызов функции «сильнее», чем оператор доступа к статическому свойству:
Пример #3 Пример вызова переменного метода со статическим свойством
class Foo
static $variable = ‘статическое свойство’ ;
static function Variable ()
echo ‘Вызов метода Variable’ ;
>
>
echo Foo :: $variable ; // Это выведет ‘статическое свойство’. Переменная $variable будет разрешена в этой области видимости.
$variable = «Variable» ;
Foo :: $variable (); // Это вызовет $foo->Variable(), прочитав $variable из этой области видимости.
Пример #4 Сложные callable-функции
$func = array( «Foo» , «bar» );
$func (); // выведет «bar»
$func = array(new Foo , «baz» );
$func (); // выведет «baz»
$func = «Foo::bar» ;
$func (); // выведет «bar»
?>
Смотрите также
User Contributed Notes 6 notes
While the documentation suggests that the use of a constant is similar to the use of a variable, there is an exception regarding variable functions. You cannot use a constant as the function name to call a variable function.
const DEBUGME =’func’;
function func($s)
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!
List of functions that accept variable arguments.
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 ()
?>
/*
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. ‘ . ‘
‘ ;
echo $obj_walker -> walker_walk () . ‘
‘ ;
echo ‘
‘ ;
echo ‘runner in action. ‘ . ‘
‘ ;
echo $obj_runner -> walker_walk () . ‘
‘ ;
echo $obj_runner -> runner_run () . ‘
‘ ;
echo $obj_runner -> xxx () . ‘
‘ ; //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.
?>
If you are here looking for a function reference, this is NOT how to do it:
function func1 ()< echo "hell0 1" ;>
$choice = func1 ; // no quotes
?>
It works, but $choice is not what you might think, a reference to a function. It is simply the name of the function as a string, written without (!) quotes.
It’s the same as
$choice = «func1» ; // with quotes
?>
You can do echo gettype($choice) to confirm.
So calling
$choice ()
?>
is a variable-function for both cases, calling it by its name, not by reference.
Go via an assigned anonymous function to get a reference to the function:
$func1 = function()< echo "hell0 1" ;>
$func1 = function()< echo "hell0 2" ;>
?>
Now you can pass around the function like a first class object
$choice = $func1 ;
?>
or
$choice = $func2 ;
?>
and call it
$choice ();
?>
If you want to pass around a class method, use the «Complex callables» from the manual, above. It’s a call by name (not a reference), but since you can include the object you can still get the flexibility you want:
class C <
function k () < echo "inside k" ;>
function j ()< echo "inside j" ; return array( $this , "k" );>>;
?>
You can use $this as the object in the first element of the array.
$c = new C ;
$c -> k ();
inside k
$func = $c -> j ();
inside j
?>
And now, le moment supreme:
$func ();
inside k
?>
A small, but helpful note. If you are trying to call a static function from a different namespace, you must use the fully qualified namespace, even if they have the same top level namespace(s). For example if you have the following class to call:
namespace Project \ TestClass ;
class Test static function funcToCall () return «test» ;
>
>
?>
You must call it as:
namespace Project \ OtherTestClass ;
class OtherTest static function callOtherFunc () $func = ‘\Project\TestClass::funcToCall’ ;
$func ();
>
>
?>
and not:
class OtherTest static function callOtherFunc () $func = ‘TestClass::funcToCall’ ;
$func ();
>
>
?>
static bar method works with statically or non statically wherese non static method could not work statically
//non static method
class myCls public function foo () echo «foo function» ;
>
static public function bar () echo «static bar function» ;
$a = new myCls ;
$myf = «foo» ;
$a -> $myf (); //works
echo «\n» ;
$a = [new myCls , «foo» ]; //works
$a ();
echo «\n» ;
//$a = [«myCls»,»foo»];//fatal error
//$a();
echo «\n» ;
//$a = «myCls::foo»;//fatal error
//$a();
echo «\n» ;
//static method called with statically or nonstatically
$b = new myCls ;
$myf = «bar» ;
$b -> $myf (); //works
echo «\n» ;
$b = [new myCls , «bar» ]; //works
$b ();
echo «\n» ;
$b = «myCls::bar» ; //works
$b ();
echo «\n» ;
$b = [ «myCls» , «bar» ]; //works
$b ();
echo «\n» ;
Php using functions with variables
To experiment on performance of pass-by-reference and pass-by-value, I used this script. Conclusions are below.
#!/usr/bin/php
function sum ( $array , $max ) < //For Reference, use: "&$array"
$sum = 0 ;
for ( $i = 0 ; $i < 2 ; $i ++)#$array[$i]++; //Uncomment this line to modify the array within the function.
$sum += $array [ $i ];
>
return ( $sum );
>
$max = 1E7 //10 M data points.
$data = range ( 0 , $max , 1 );
$start = microtime ( true );
for ( $x = 0 ; $x < 100 ; $x ++)$sum = sum ( $data , $max );
>
$end = microtime ( true );
echo «Time: » .( $end — $start ). » s\n» ;
/* Run times:
# PASS BY MODIFIED? Time
— ——- ——— —-
1 value no 56 us
2 reference no 58 us
3 valuue yes 129 s
4 reference yes 66 us
1. PHP is already smart about zero-copy / copy-on-write. A function call does NOT copy the data unless it needs to; the data is
only copied on write. That’s why #1 and #2 take similar times, whereas #3 takes 2 million times longer than #4.
[You never need to use &$array to ask the compiler to do a zero-copy optimisation; it can work that out for itself.]
2. You do use &$array to tell the compiler «it is OK for the function to over-write my argument in place, I don’t need the original
any more.» This can make a huge difference to performance when we have large amounts of memory to copy.
(This is the only way it is done in C, arrays are always passed as pointers)
3. The other use of & is as a way to specify where data should be *returned*. (e.g. as used by exec() ).
(This is a C-like way of passing pointers for outputs, whereas PHP functions normally return complex types, or multiple answers
in an array)
5. Sometimes, pass by reference could be at the choice of the caller, NOT the function definitition. PHP doesn’t allow it, but it
would be meaningful for the caller to decide to pass data in as a reference. i.e. «I’m done with the variable, it’s OK to stomp
on it in memory».
*/
?>