What is the format of the variables in the return value?

Question

I am a new learner of php. I found a piece of code:

if($x < time()){
     return [false,'error'];
}

The logic or variables don't matter, but I don't understand how [false,'error'] works. Is it a boolean, an array, or...?

Answer 1

This is an array. It has two elements of two different types. The first element type is Boolean. The second element is a string.

Arrays in PHP can contain elements of different types.