What is the potential cause of the warning "shuffle() expects parameter 1 to be array, null given" in PHP when using the shuffle function on an array?

The warning "shuffle() expects parameter 1 to be array, null given" occurs when the shuffle function in PHP is called with a null value instead of an array. To solve this issue, ensure that the parameter passed to the shuffle function is indeed an array and not null. You can check if the array is null before calling the shuffle function to prevent this warning.

// Check if the array is not null before shuffling
if ($array !== null) {
    shuffle($array);
}