What does the yield operator do?

The `yield` operator in PHP is used to create generators. Generators are a special type of objects that allow you to iterate through a set of values without the need to store all values in memory. Instead, generators produce values on the fly as requested.

The basic idea of `yield` is that it suspends the execution of the function and returns a value to the calling code. Upon the next generator call, it resumes execution from the suspension point and continues generating the next value.

Here's an example of a simple generator in PHP:

                        
function myGenerator() {
    yield 1;
    yield 2;
    yield 3;
}

// Calling the generator
$generator = myGenerator();

foreach ($generator as $value) {
    echo $value . ' ';
}

// Output: 1 2 3

                        
                    

In this example, the `myGenerator` generator contains three `yield` statements, generating a sequence of numbers. When the generator is called and iterated through using foreach, it outputs the sequence of numbers 1, 2, and 3.

Generators are particularly useful when working with large datasets or when processing values one at a time without using a significant amount of memory.