Add unique random value from array

Question

I'm trying to generate a unique random value from an array and store it in another array so it can't be used again.

I've managed to generate the random value based on a meta field but I'm not sure how I would go about making this unique and ensuring the same values aren't being generated again. I've created an empty array $tickethistory to save the values into. Is it possible the next time it runs to run a validation check so the $lottery_max_tickets don't include the $tickethistory values?

I'm using the function below which returns the number and I', calling it when customers purchase a product in Woocommerce.

function add_lottery_ticket_number( $postid ) {
    $tickethistory = array();
    $lottery_max_tickets = get_post_meta( $postid, '_max_tickets', true );
    $max_tickets = range(1, $lottery_max_tickets);

    $ticketallocated = array_rand($max_tickets, 1);
    $tickethistory[] = $ticketallocated;

    return $ticketallocated;
}


for ( $i = 0; $i < $item_meta['_qty'][0]; $i++ ) {
    add_post_meta( $product_id, '_participant_id', $order->get_user_id() );
    $participants = get_post_meta( $product_id, '_lottery_participants_count', true ) ? get_post_meta( $product_id, '_lottery_participants_count', true ) : 0;
    update_post_meta( $product_id, '_lottery_participants_count', intval( $participants ) + 1 );
    $this->add_lottery_to_user_metafield( $product_id, $order->get_user_id() );
    $ticketnumber = $this->add_lottery_ticket_number($product_id);
    $log_ids[] = $this->log_participant( $product_id, $order->get_user_id(), $ticketnumber, $order_id, $item );
}

Can you save the history in the for-loop scope? I mean - do you want it to be unique for each i or for bigger scope? — dWinder
– dWinder, Commented Jan 8, 2019 at 17:30
Hi David, I want it to be unique for each i and the bigger scope. So when a new customer purchases the same product, they won't be able to have numbers which are already allocated to a different customer. They also need to be unique for an individual purchase so if they have 10 items, it will generate 10 unique numbers. Does that make sense? — Shaun
– Shaun, Commented Jan 8, 2019 at 17:57
Hi David, I haven't been able to test it yet but looks like it will work. Thanks so much — Shaun
– Shaun, Commented Jan 9, 2019 at 10:43

dWinder · Accepted Answer · 2019-01-08 19:17:47Z

1

As you can see here, you can use storing array in the metadata - in your case, the tickethistory array.

But, for your case I would take different approach - create ticket options once and assign the first element each time.

Consider the following:

function add_lottery_ticket_number( $postId ) {
    if (metadata_exists('post', $postId, 'optionsToGive')) {
        $ticketOptions = get_post_meta( $postId, 'optionsToGive', true );
    } else {
        $lottery_max_tickets = get_post_meta( $postid, '_max_tickets', true );
        $ticketOptions = range(1, $lottery_max_tickets);
        shuffle($ticketOptions ); //random order of all number
    }
    $ticketAllocated = array_shift($ticketOptions); //take the first element
    update_post_meta( $postId, 'optionsToGive', $ticketOptions ); //update all the rest
    return $ticketAllocated;
}

Notice, if all numbers has been assign this will return null.

As I never tested this code please consider it as pseudo.

edited Jan 8, 2019 at 19:17

answered Jan 8, 2019 at 18:18

dWinder

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2 Comments

Shaun Over a year ago

Just a quick question - What benefits does metadeta_exists have over empty or isset?

dWinder Over a year ago

I have no huge experience in metadata method but it seems good practice to check exist then to use get_post_meta and check if empty

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