如何将一组变量传递给类

Question

This may be a bit of an XY questions, so I'm going to explain what I'm trying to do first. I'm attempting to create a single php file to handle all of my page refresh AJAX calls. That means I want to be able to send it a class name, plus a list of the variables that the class constructor takes, and for it to then create the class.

I can create the class fine. $class = new $className(); works just fine for creating the class. The problem is passing in the default variables. Most of the variables are objects containing other classes, so I can't just include this once the class is created, I need to pass them as the class is created.

I was thinking something along the lines of:

$varStr = '';
$s = '';
foreach($vars as $var) {
    switch($var['type']) {
        case 'object':
            $varStr .= $s . '$' . $var['value'];
            break;
        case 'variable':
            $varStr .= $s . $var['value'];
    }
    $s = ',';
}
$class = new $className(echo $varStr);

Now obviously echo $varStr isn't going to work there, but I have no idea what will. Is there anything I can do that will output the variables from my array into the class constructor like that? Is what I'm trying to do even possible? Is there a better way?

Whilst I understand I could just pass the whole array to the class constructor, this would complicate the main part of the program, and I would rather just ditch the idea of a single page for AJAX refresh than go down that route.

Answer 1

So basically you're trying to pass a variable number of arguments to a constructor? In a regular function, you could do something like:

function foo() {
    $args = func_get_args();
    ...
}

call_user_func_array('foo', array('bar', 'baz'));

This won't work for constructors, since the calling mechanism is different. You could do:

class Foo {

    public function __construct() {
        $args = func_get_args();
        ...
    }

}

$class = new ReflectionClass('Foo');
$obj = $class->newInstanceArgs(array('bar', 'baz'));

But really, what you should be doing is this:

class Foo {

    public function __construct(array $args) {
        ...
    }

}

$obj = new Foo(array('bar', 'baz'));

or

class Foo {

    public function __construct($bar, $baz) {
        ...
    }

}

$obj = new Foo('bar', 'baz');

Anything else is quite insane. If your object constructor is so complicated, you probably need to simplify it.

Answer 2

This is a wild guess at what you're trying to do but maybe this is what you're after:

// Generate constructor args

$args = array();
foreach($vars as $var) {
    switch($var['type']) {
        $value = $var['value'];
        case 'object':
            args[] = ${$value};     // evaluate, I think that's what you want?
            break;
        case 'variable':
            args[] = $value;        // use as is
            break;
    }

}

// Instanciate class with args
$class = new ReflectionClass($className);
$obj = $class->newInstanceArgs($args);

For this to work, it would require $vars to enumerates args in the correct order expected by each class constructor.