User Contributed Notes in variable functions

example:

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.

example:

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:

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
04-May-2005 01:34
This can quite useful for a dynamic database class:

(Note: This just a simplified section)

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.

example:

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');

example:

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");
}

example:

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 04:11
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 02:18
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"