PHP recursive function is not working right [duplicate]

Question

I am running a function, and part of it requires to pick a random number. However, it cannot be in an array of already selected numbers. So if the random number chosen is in the array, it needs to select a new number. I seem to be really struggling with something that seems so easy.

function choice() {
    global $countries;
    global $count;
    global $answers;
    global $choice;

    $i = rand(0, $count - 1);
    if(in_array($i, $answers))
        choice();
    else {
        $answers[] = $i;
        $choice = $countries[$i]['capital_city'];
        return $choice;
    }

So the current logic here, is it selects a random number, checks if it’s in the array. If it isn’t then it sets the variable and returns it. If it is, then it generates a new number by restarting the function. When it does find one in the function, it returns an empty result, rather than going back through the function. What am I doing so wrong?

We can't someone who doesn't help us first by telling us what the precise error and location is — Andrew Li
– Andrew Li, Commented Jun 28, 2016 at 23:23
have a look at this question, seems very similar: stackoverflow.com/a/17110791/1823684 — Terry Kernan
– Terry Kernan, Commented Jun 28, 2016 at 23:25
You know functions can take arguments, right? Use of globals is generally a bad thing and should only be used when that is your last possible pragmatic choice. — Mulan
– Mulan, Commented Jun 28, 2016 at 23:47

Rizier123 · Accepted Answer · 2016-06-28 23:45:03Z

2

Add a return statement before the recursive call.

function choice() {
    global $countries;
    global $count;
    global $answers;
    global $choice;

    $i = rand(0,$count-1);

    if(in_array($i,$answers)) return choice();
    else {
        $answers[] = $i;
        $choice = $countries[$i]['capital_city'];
        return $choice;
    }

edited Jun 28, 2016 at 23:45

Rizier123

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answered Jun 28, 2016 at 23:35

etherealite

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5 Comments

Source Over a year ago

That seems to work, I knew i was missing something simple like that, but I couldnt work it out.

Source Over a year ago

However, what is better, this way, or using a while loop?

atoms Over a year ago

I believe the while loop will have less overhead. Would also use references in place of global

Mulan Over a year ago

@Source the "correct" answer is meaningless if this is the code you end up with.

etherealite Over a year ago

@naomik No regrets, #globals for life.

Peter Mortensen · Accepted Answer · 2022-05-27 13:19:29Z

2

If you don’t need to use recursion, you could just use a while loop:

function choice() {
    global $countries;
    global $count;
    global $answers;
    global $choice;

    $i = rand(0, $count - 1);

    while (in_array($i, $answers)) {
        $i = rand(0, $count - 1);
    }

    $answers[] = $i;
    $choice = $countries[$i]['capital_city'];
    return $choice;
}

Or use this do while in place of the while;

do {
    $i = rand(0, $count-1);
} while (in_array($i, $answers));

edited May 27, 2022 at 13:19

Peter Mortensen

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answered Jun 28, 2016 at 23:32

atoms

3,1032 gold badges25 silver badges46 bronze badges

2 Comments

Source Over a year ago

count value didnt need to be altered.

Rizier123 Over a year ago

I think a do while loop would maybe look a bit better here :)

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