Question

I would like to ask, if there is a way, to use variables in a class, that were declared out of it.

Example:

$foo = 'bar';
class foobar{
    function example(){
        echo "foo{$foo}";
    }
}
$foobar = new foobar;
$foobar->example();

This code produces a notice: Notice: Undefined variable: foo
Is there a way to make it work? Or is there some work-around?

Answer 1

Use a construct to import it or use the global keyword. You could do something like this:

$var = 'value';
class foobar {
    private $classVar;
    function __construct($param) {
        $this->classVar = $param;
    }
}

And initiate it like this:

$var = 'value';
$inst = new foobar($var);

Or you can use global variables (which I wouldn’t recommend in this case) and do something like this:

$var = 'value';
class foobar {
    global $var;
    function show() {
       echo $var;
    }
}

UPDATE: To use a class within another class, it may be instantiated in the constructor if its instance is needed throughout implementation, or it may be instantiated only when needed.

To create a reference to another class inside the constructor, do something like this:

class class1 {
    private $someVar;

    function __construct() {
        $this->someVar = 'success';
    }

    function doStuff() {
        return $this->someVar;
    }
}

class class2 {
    private $ref;
    private $val;
    function __construct() {
        $this->ref = new class1();
        $this->val = $this->ref->doStuff();
        // $this->val now holds the value 'success'
    }
}

$inst = new class2(); // upon calling this, the $val variable holds the value 'success'

Or you can call it only when needed, like so:

class class1 {
    private $someVar;

    function __construct() {
        $this->someVar = 'success';
    }

    function doStuff() {
        return $this->someVar;
    }
}

class class2 {
    private $ref;
    private $val;
    function __construct() {
        // do something
    }
    function assign() {
        $this->ref = new class1();
        $this->val = $this->ref->doStuff();
        // $this->val now holds the value 'success'
    }
}

$inst = new class2(); // the $val variable holds no value yet
$inst->assign(); // now $val holds 'success';

Hope that helps you.