Explanation of PHP array foreach scope within function

Question

I have the following PHP code:

$car1 = new Car('Ford','Fusion');
$car2 = new Car('Chevy', 'Avalanche');
$car3 = new Car('Ford', 'F150');

$cars = array($car1, $car2, $car3);

function getCarsByMake($carMake){
    foreach($cars as $car){
        if($car->make == $carMake){
            echo 'Car: ' . $car->make . ' ' . $car->model . "<br>";
        }
    }
}

getCarsByMake('Ford');

I get the error that $cars in the foreach statement is undefined. However, as I understand it, the $cars array should be global in scope? If I pass the array into the function through the constructor it works fine. But I'm wondering why I can't access the array in this way.

use global $cars; inside the function. Just above foreach loop — Sahil Gulati
– Sahil Gulati, Commented Jul 21, 2017 at 16:30
function is just like a room, and the cars is outside the room, so you need to drag the car to the room so you can modify it inside the room — Atmahadli
– Atmahadli, Commented Jul 21, 2017 at 16:37
Passing the $cars into the function makes it a lot easier to test, you can pass in various versions to check the function reacts as it should. — Nigel Ren
– Nigel Ren, Commented Jul 21, 2017 at 16:50

GrumpyCrouton · Accepted Answer · 2017-07-21 16:36:15Z

6

Along with Exprator's solution, you could also pass the $cars array to the function like this.

function getCarsByMake($carMake, $cars){
    foreach($cars as $car){
        if($car->make == $carMake){
            echo 'Car: ' . $car->make . ' ' . $car->model . "<br>";
        }
    }
}

getCarsByMake('Ford', $cars);

edited Jul 21, 2017 at 16:36

answered Jul 21, 2017 at 16:33

GrumpyCrouton

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2 Comments

Reed Over a year ago

Yep, I made a note in my original post that this method did work for me, I was just wondering about the scope of the variable itself. Thanks!

GrumpyCrouton Over a year ago

@Reed You should accept an answer, whichever one works the best in your case.

Marvin · Accepted Answer · 2017-07-21 16:44:11Z

3

You have two options.

Add the global keyword

function getCarsByMake($carMake){
   global $cars;
   foreach($cars as $car){
       if($car->make == $carMake){
           echo 'Car: ' . $car->make . ' ' . $car->model . "<br>";
       }
   }
}

Use the $GLOBALS array:

function getCarsByMake($carMake){
    foreach($GLOBALS["cars"] as $car){
        if($car->make == $carMake){
            echo 'Car: ' . $car->make . ' ' . $car->model . "<br>";
        }
    }
}

Although I'd still recommend passing it as an explicit parameter as that makes the code more readable and maintainable, IMHO.

edited Jul 21, 2017 at 16:44

answered Jul 21, 2017 at 16:35

Marvin

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2 Comments

Reed Over a year ago

Any reason why you'd suggest using it as a parameter? Another user advised another method over it.

Marvin Over a year ago

Because IMHO it makes the code less readable and less maintainable. Within your function you can never be sure where the global variable comes from and where (or if) it is initialized. And from outside it is not obvious to a caller that the function needs and works on the global variable cars.

Exprator · Accepted Answer · 2017-07-21 16:32:06Z

3

function getCarsByMake($carMake){
    global $cars;
    foreach($cars as $car){
        if($car->make == $carMake){
            echo 'Car: ' . $car->make . ' ' . $car->model . "<br>";
        }
    }
}

getCarsByMake('Ford');

its because the function is not getting the $cars , you need to globally access it inside the function

answered Jul 21, 2017 at 16:32

Exprator

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3 Comments

Reed Over a year ago

Is there any explanation to this besides just being a nature of the language?

GrumpyCrouton Over a year ago

@Reed Your variable is not in the global scope unless declared global.

Exprator Over a year ago

the reason is OOPs @Reed

rowmoin · Accepted Answer · 2017-07-21 17:52:53Z

0

You can call $cars globally but you can also try by another way according to your code.Ex:

$car1 = new Car('Ford','Fusion');
$car2 = new Car('Chevy', 'Avalanche');
$car3 = new Car('Ford', 'F150');

$cars = array($car1, $car2, $car3);

function getCarsByMake($carMake,$cars){
    foreach($cars as $car){
        if($car->make == $carMake){
            echo 'Car: ' . $car->make . ' ' . $car->model . "<br>";
        }
    }
}

getCarsByMake('Ford',$cars);

edited Jul 21, 2017 at 17:52

answered Jul 21, 2017 at 16:49

rowmoin

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