Question

How can I define a variable before or while initializing the class?

<?php
class class{
 public $var;
 public function __construct(){
  echo $this -> var;
 }
}
$class = new class;
$class -> var = "var";
?>

Answer 1

If you mean instantiating the class, then use the constructor:

class Foo {

    private $_bar;

    public function __construct($value) {
        $this->_bar = $value;
    }

}

$test = new Foo('Mark');