The Uncallable Function¶

<?php

function foo() {
    echo __METHOD__;
    yield 1;
}

foo(); // displays nothing, no code is executed
echo 'the end'; // displays the end

?>

The function foo() cannot be called. When the code does so, nothing happens.

The trick is the inclusion of a call to yield (or yield from) in the function. It turns the function into a generator, and calling it directly does nothing. It needs to be called with foreach() or iterator_to_array().

This trick applies to functions, arrow functions, closures and methods.

See Also¶

Generators (PHP manual)
The function that cannot execute [Try me]

PHP Features¶

Last updated: 14 July 2026