PHP: How to instantiate a class with arguments from within another class

Question

Hello All,

I am in a situations where i need to instantiate a class with arguments from within an instance of another class. Here is the prototype:

//test.php

class test
{
 function __construct($a, $b, $c)
 {
  echo $a . '<br />';
  echo $b . '<br />';
  echo $c . '<br />';
 }
}

Now, i need to instantiate above class using below class's cls function:

class myclass
{
function cls($file_name, $args = array())
{
 include $file_name . ".php";

 if (isset($args))
 {
  // this is where the problem might be, i need to pass as many arguments as test class has.
  $class_instance = new $file_name($args);
 }
 else
 {
  $class_instance = new $file_name();
 }

 return $class_instance;
}
}

Now when i try to create an instance of test class while passing arguments to it:

$myclass = new myclass;
$test = $myclass->cls('test', array('a1', 'b2', 'c3'));

It gives error: Missing argument 1 and 2; only first argument is passed.

This works fine if i instantiate a class which has no arguments in it's constructor function.

For experienced PHP developers, above should not be much of a problem. Please help.

Thanks

Answer 1

You can:

1) Modify test class to accept an array, which contains the data you wish to pass.

//test.php

class test
{
        function __construct($a)
        {
                echo $a[0] . '<br />';
                echo $a[1] . '<br />';
                echo $a[2] . '<br />';
        }
}

2) initiate using a user method instead of the constructor and call it using the call_user_func_array() function.

//test.php

class test
{
        function __construct()
        {

        }

        public function init($a, $b, $c){
                echo $a . '<br />';
                echo $b . '<br />';
                echo $c . '<br />';
        }

}

In your main class:

class myclass
{
function cls($file_name, $args = array())
{
        include $file_name . ".php";

        if (isset($args))
        {
                // this is where the problem might be, i need to pass as many arguments as test class has.
                $class_instance = new $file_name($args);
                call_user_func_array(array($class_instance,'init'), $args);
        }
        else
        {
                $class_instance = new $file_name();
        }

        return $class_instance;
}
}

http://www.php.net/manual/en/function.call-user-func-array.php

Lastly, you can leave your constructor params blank and use func_get_args().

//test.php

class test
{
        function __construct()
        {
                $a = func_get_args();
                echo $a[0] . '<br />';
                echo $a[1] . '<br />';
                echo $a[2] . '<br />';
        }
}

http://sg.php.net/manual/en/function.func-get-args.php

Answer 2

You could use call_user_func_array() I believe.

or you could leave the arguments list of the constructor, and then inside the constructor use this

$args = func_get_args();

Answer 3

you need Reflection http://php.net/manual/en/class.reflectionclass.php

if(count($args) == 0)
   $obj = new $className;
else {
   $r = new ReflectionClass($className);
   $obj = $r->newInstanceArgs($args);
}