How to Generate Random Numbers without Repetition for a Comprehensive Listing Randomizer?

Generating Random Numbers without Repetition: A Comprehensive Guide

In your quest to develop a website that randomizes Yelp listings, you seek a method that ensures all 20 listings are displayed once before any repetition occurs. Let's explore a range of approaches to address this challenge.

PHP's rand(0, 19) Approach

Your current implementation uses PHP's rand(0, 19) to generate a random index for selecting a Yelp listing. However, this method has a limitation: it can repeat numbers. To overcome this, we need a more sophisticated approach.

Shuffling a Range of Numbers

One effective solution is to shuffle a range of numbers representing the listing indices. This can be achieved using range() and shuffle() as follows:

<code class="php">$numbers = range(0, 19);
shuffle($numbers);</code>

This creates an array containing numbers from 0 to 19 in random order.

Alternative Solution Using randomGen() Function

Another approach is to employ a custom randomGen() function that accepts a minimum, maximum, and quantity as parameters. It generates a list of unique random numbers within the specified range:

<code class="php">function randomGen($min, $max, $quantity) {
    $numbers = range($min, $max);
    shuffle($numbers);
    return array_slice($numbers, 0, $quantity);
}

print_r(randomGen(0, 20, 20));  // generates 20 unique random numbers</code>

Storing Used Numbers and Updating in a Database

To ensure that all listings are shown without repetition, you can store the displayed listings in a database. Each time you display a random listing, check if its ID matches any in the database. If not, display the listing and add its ID to the database. Repeat this process until all listings have been displayed.

This method ensures that each listing is displayed exactly once before any repetition occurs.

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