Generator Return Expressions in PHP 7

In PHP 7, generator functions can now return expressions using the return statement. This enhancement allows generators to yield values during iteration and then return a final value when the generator completes execution.

Key Features

Generator return expressions in PHP 7 provide the following capabilities −

• Return a final value from a generator function after all yields are completed
• Retrieve the returned value using the Generator::getReturn() method
• Only expression values can be returned, not references
• The return value is accessible once the generator has finished yielding all values

Basic Example

Here's a simple example demonstrating generator return expressions −

<?php
    $generator = (function(){
        yield "five";
        yield "six";
        yield "seven";
        return "eight";
    })();
    
    foreach ($generator as $val) {
        echo $val . "<br>";
    }
    
    echo "Return value: " . $generator->getReturn() . "<br>";
?>

five
six
seven
Return value: eight

Named Generator Function

You can also use named generator functions with return expressions −

<?php
    function gen() {
        yield 'A';
        yield 'B';
        yield 'C';
        return 'gen-return';
    }
    
    $generator = gen();
    
    foreach ($generator as $letter) {
        echo $letter . " ";
    }
    
    echo "\nGenerator return: " . $generator->getReturn();
?>

A B C 
Generator return: gen-return

Important Notes

• The getReturn() method can only be called after the generator has finished execution
• Calling getReturn() before the generator completes will throw an exception
• Generator return expressions work with any data type − strings, arrays, objects, etc.

Conclusion

Generator return expressions in PHP 7 enhance the functionality of generators by allowing them to return a final value. This feature is particularly useful for aggregating results or providing status information after processing all yielded values.