(PHP 5 >= 5.1.0, PHP 7, PHP 8)
iterator_apply — Call a function for every element in an iterator
Calls a function for every element in an iterator.
iteratorThe iterator object to iterate over.
callback
       The callback function to call on every element.
       This function only receives the given args, so it
       is nullary by default. If count($args) === 3, for
       instance, the callback function is ternary.
       
Note: The function must return
truein order to continue iterating over theiterator.
args
       An array of arguments; each element of
       args is passed to the callback
       callback as separate argument.
      
Returns the iteration count.
Example #1 iterator_apply() example
<?php
function print_caps(Iterator $iterator) {
    echo strtoupper($iterator->current()) . "\n";
    return TRUE;
}
$it = new ArrayIterator(array("Apples", "Bananas", "Cherries"));
iterator_apply($it, "print_caps", array($it));
?>
The above example will output:
APPLES BANANAS CHERRIES