How to generate a random number in PHP

Posted on Jul 18, 2022

Learn how to generate a random number in PHP, with code examples

Photo from Unsplash

To generate a random number using PHP, you need to call the rand() function in your script.

The rand() function returns an int integer number between 0 and getrandmax() function result.

Let’s call the rand() function and print the value using echo:

echo rand(); // 978288474
echo rand(); // 1344295660

You will see a different number printed for each time you call the rand() function.

You can set the minimum and maximum number the rand() function will generate by passing the $min and $max arguments:

rand(int $min, int $max): int

For example, to random between 10 to 30:

echo rand(10, 30); // random between 10 to 30

You can also generate a random negative number as shown below:

echo rand(-39, -12); // random between -39 to -12

The rand() function has inclusive behavior, which means the $min and $max numbers are included in the random selection.

In PHP version 7.1, the rand() function is an alias for the mt_rand() function.

The mt_rand() function is generates a random number using the Mersenne Twister algorithm, which has been tested to be faster and gives more random results (less duplicate in the returned integer) than the rand() function.

The rand() function allows you to reverse the $min and $max arguments.

When you pass a $max number that is less than the $min number, the function will work the same:

echo rand(10, 5); // random 5 to 10
echo mt_rand(10, 5); // Uncaught ValueError

Calling mt_rand() with a lesser $max value will return false and throw the following warning:

Warning: Uncaught ValueError: mt_rand(): 
Argument #2 ($max) must be greater than or 
equal to argument #1 ($min) in php shell code:1

When you’re using PHP v7.1 and above, the rand() function is backward compatible.

The function will not return false when the $max number is lesser than $min.

And that’s how you generate a random number using PHP 👍

Level up your programming skills

I'm sending out an occasional email with the latest programming tutorials. Drop your email in the box below and I'll send new stuff straight into your inbox!

No spam. Unsubscribe anytime.