Връщане на стойности
It may be useful to note that 'variable functions' can only be used in conjunction with functions, and not language constructs such as echo, die, exit, etc.
Променливи функции
PHP поддържа концепцията за променливи функции. Това означава, че ако дадена променлива има скоби в края си, PHP ще потърси за функция с име - стойността на променливата и ще се опита да я изпълни. Освен за друго, това може да бъде използвано и с цел осъществяване на обратни извиквания, функционални таблици и други.
Променливите функции няма да работят с езикови конструкции като echo(), print(), unset(), isset(), empty(), include(), require() и други от този род. Трябва да създадете ваша собствена функция като опаковка, за да можете да използвате някоя от тези езикови конструкции като променлива функция.
Example #1 Пример за променлива функция
<?php
function foo() {
echo "Във foo()<br />\n";
}
function bar($arg = '')
{
echo "В bar(); аргументът беше '$arg'.<br />\n";
}
// Това е функция-опаковка на echo
function echoit($string)
{
echo $string;
}
$func = 'foo';
$func(); // Това извиква foo()
$func = 'bar';
$func('test'); // Това извиква bar()
$func = 'echoit';
$func('test'); // Това извиква echoit()
?>
Можете също да извиквате и методи на обекти, посредством синтаксиса за променливи функции.
Example #2 Пример за променлив метод
<?php
class Foo
{
function Variable()
{
$name = 'Bar';
$this->$name(); // Това извиква метода Bar()
}
function Bar()
{
echo "Това е Bar";
}
}
$foo = new Foo();
$funcname = "Variable";
$foo->$funcname(); // Това извиква $foo->Variable()
?>
Вж. също call_user_func(), променливи променливи и function_exists().
add a note
User Contributed NotesПроменливи функции
mike at mike-griffiths dot co dot uk
27-Jun-2007 04:37
27-Jun-2007 04:37
boards at gmail dot com
22-Jan-2006 07:07
22-Jan-2006 07:07
If you want to call a static function (PHP5) in a variable method:
Make an array of two entries where the 0th entry is the name of the class to be invoked ('self' and 'parent' work as well) and the 1st entry is the name of the function. Basically, a 'callback' variable is either a string (the name of the function) or an array (0 => 'className', 1 => 'functionName').
Then, to call that function, you can use either call_user_func() or call_user_func_array(). Examples:
<?php
class A {
protected $a;
protected $c;
function __construct() {
$this->a = array('self', 'a');
$this->c = array('self', 'c');
}
static function a($name, &$value) {
echo $name,' => ',$value++,"\n";
}
function b($name, &$value) {
call_user_func_array($this->a, array($name, &$value));
}
static function c($str) {
echo $str,"\n";
}
function d() {
call_user_func_array($this->c, func_get_args());
}
function e() {
call_user_func($this->c, func_get_arg(0));
}
}
class B extends A {
function __construct() {
$this->a = array('parent', 'a');
$this->c = array('self', 'c');
}
static function c() {
print_r(func_get_args());
}
function d() {
call_user_func_array($this->c, func_get_args());
}
function e() {
call_user_func($this->c, func_get_args());
}
}
$a =& new A;
$b =& new B;
$i = 0;
A::a('index', $i);
$a->b('index', $i);
$a->c('string');
$a->d('string');
$a->e('string');
# etc.
?>
Storm
03-May-2005 05:34
03-May-2005 05:34
This can quite useful for a dynamic database class:
(Note: This just a simplified section)
<?php
class db {
private $host = 'localhost';
private $user = 'username';
private $pass = 'password';
private $type = 'mysqli';
public $lid = 0;
// Connection function
function connect() {
$connect = $this->type.'_connect';
if (!$this->lid = $connect($this->host, $this->user, $this->pass)) {
die('Unable to connect.');
}
}
}
$db = new db;
$db->connect();
?>
Much easier than having multiple database classes or even extending a base class.
ian at NO_SPAM dot verteron dot net
20-Dec-2002 04:33
20-Dec-2002 04:33
A good method to pass around variables containing function names within some class is to use the same method as the developers use in preg_replace_callback - with arrays containing an instance of the class and the function name itself.
function call_within_an_object($fun)
{
if(is_array($fun))
{
/* call a function within an object */
$fun[0]->{$fun[1]}();
}
else
{
/* call some other function */
$fun();
}
}
function some_other_fun()
{
/* code */
}
class x
{
function fun($value)
{
/* some code */
}
}
$x = new x();
/* the following line calls $x->fun() */
call_within_an_object(Array($x, 'fun'));
/* the following line calls some_other_fun() */
call_within_an_object('some_other_fun');
madeinlisboa at yahoo dot com
05-Sep-2002 02:14
05-Sep-2002 02:14
Finally, a very easy way to call a variable method in a class:
Example of a class:
class Print() {
var $mPrintFunction;
function Print($where_to) {
$this->mPrintFunction = "PrintTo$where_to";
}
function PrintToScreen($content) {
echo $content;
}
function PrintToFile($content) {
fputs ($file, $contents);
}
.. .. ..
// first, function name is parsed, then function is called
$this->{$this->mPrintFunction}("something to print");
}
msmith at pmcc dot com
03-May-2002 01:49
03-May-2002 01:49
Try the call_user_func() function. I find it's a bit simpler to implement, and at very least makes your code a bit more readable... much more readable and simpler to research for someone who isn't familiar with this construct.
anpatel at NOSPAM_cbu dot edu
18-Mar-2002 06:11
18-Mar-2002 06:11
Yes interpolation can be very tricky. I suggest that you always use parenthesis, or curly brackets(whichever applies) to make your expression clear.
Dont ever depend on a language's expression parse preference order.
retro at enx dot org
14-Jan-2002 04:18
14-Jan-2002 04:18
Another way to have php parse a variable within an object as a function is to simply set a temporary variable to its value. For example:
$obj->myfunction = "foo";
$x = $obj->myfunction;
$x(); // calls the function named "foo"