Hướng dẫn name variable php

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

function foo() {
    echo "In foo()\n";
}

function

Object methods can also be called with the variable functions syntax.

Example #2 Variable method example

class Foo
{
    function Variable()
    {
        $name = 'Bar';
        $this->$name(); // This calls the Bar() method
    }

        function

When calling static methods, the function call is stronger than the static property operator:

Example #3 Variable method example with static properties

class Foo
{
    static $variable = 'static property';
    static function Variable()
    {
        echo 'Method Variable called';
    }
}

echo

Example #4 Complex callables

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 ¶

3 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!

Anonymous ¶

11 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.
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()
?>

rnealxp at yahoo dot com ¶

2 years ago

/*
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.
*/

anisgazig at gmail dot com ¶

6 months ago

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";

            }
}

Anonymous ¶

2 years ago

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

josh at joshstroup dot xyz ¶

6 years ago

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();
    }
}
?>