iterator_apply

    (PHP 5 >= 5.1.0, PHP 7, PHP 8)

    iterator_apply — Call a function for every element in an iterator

    Description

    iterator_apply(Traversable $iterator, callable $callback, ?array $args = null): int

    Calls a function for every element in an iterator.

    Parameters

    iterator

    The 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 true in order to continue iterating over the iterator.

    args

    An array of arguments; each element of args is passed to the callback callback as separate argument.

    Return Values

    Returns the iteration count.

    Examples

    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

    See Also

    • array_walk() - Apply a user supplied function to every member of an array

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    User Contributed Notes 3 notes

    up
    2
    tezcatl at fedoraproject dot org
    6 years ago
    Each of the arguments required by the function, must be in the array supplied in the third argument to iterator_apply. You can use references too. Example:

    <?php

    function translate_to(string $target_language, Iterator $words, array $dictionaries) {

    $language = ucfirst($target_language);
    $dictionary = $dictionaries[$target_language] ?? 'not found';

    if (    $dictionary === 'not found') {
    echo     "Not found dictionary for {$language}\n";
    return;
    }

    echo     "English words translated to {$language}\n";

    $not_found = [];

    iterator_apply($words, function($words, $dictionary, &$not_found){

    $english_word = $words->current();

    $translated_word = $dictionary[$english_word] ?? '';

    if (    $translated_word !== '') {
    echo     "{$english_word} translates to {$translated_word}\n";
    } else {
    $not_found[] = $english_word;
    }

    return     true;

    }, array(    $words, $dictionary, &$not_found));

    echo     "\nNot found words:\n" . implode("\n", $not_found) . "\n";
    }

    $dictionaries = [
    'nahuatl' => [
    'one' => 'Ze',
    'two' => 'Ome',
    'three' => 'Yei',
    'four' => 'Nahui',
    ],
    ];

    $iterator = new \ArrayIterator(array('one', 'two', 'three', 'four', 'gasoil'));

    translate_to('nahuatl', $iterator, $dictionaries);
    ?>

    English words translated to Nahuatl
    one translates to Ze
    two translates to Ome
    three translates to Yei
    four translates to Nahui

    Not found words:
    gasoil
    up
    1
    tezcatl at fedoraproject dot org
    6 years ago
    Be aware of the proper methods to iterate the specific Iterator you are consuming, as the implementation of the method could vary its behaviour.

    For example, unlike the ArrayIterator, you can't iterate on a SplDoubleLinkedList with current() without using next() on every iteration (and then, only would iterate if you return true at the end of the callable. It is far easier then with LinkedLists use a while($it->valid()) { $it->current(); $it->next(); }

    Let's see:

    <?php

    $ll     = new \SplDoublyLinkedList();

    $ll->push('ze');
    $ll->push('ome');
    $ll->push('yei');
    $ll->push('nahui');

    $ll->rewind();

    $iterations_done = iterator_apply($ll, function(Iterator $it) {

    echo     implode("\t=>", [
    $it->key(),
    $it->current(),
    ucfirst($it->current())
    ]),    "\n";

    return     true;

    }, array(    $ll));

    echo     "Did iterate {$iterations_done} times \n";

    $ll->rewind();

    $iterations_done = iterator_apply($ll, function(Iterator $it) {

    echo     implode("\t=>", [
    $it->key(),
    $it->current(),
    ucfirst($it->current())
    ]),    "\n";

    $it->next();

    return     true;

    }, array(    $ll));

    echo     "Did iterate {$iterations_done} times \n";

    $ll->setIteratorMode(SplDoublyLinkedList::IT_MODE_FIFO | SplDoublyLinkedList::IT_MODE_DELETE);

    var_dump($ll->count());

    foreach(    $ll as $key => $val) {
    echo     "{$key}\t",ucfirst($val),"\n";
    }

    var_dump($ll->count());
    ?>

    Output:

    0 =>ze =>Ze
    0 =>ze =>Ze
    0 =>ze =>Ze
    0 =>ze =>Ze
    Did iterate 4 times
    0 =>ze =>Ze
    1 =>ome =>Ome
    2 =>yei =>Yei
    3 =>nahui =>Nahui
    Did iterate 4 times
    int(4)
    0 Ze
    0 Ome
    0 Yei
    0 Nahui
    int(0)
    up
    -2
    ycgambo at outlook dot com
    6 years ago
    $args is an array and each of its elements are passed to the callback as separate arguments.

    so this is the right way to get args:

    <?php
    $ai     = new ArrayIterator(range(0, 2));

    iterator_apply($ai, function() {
    var_dump(func_get_args()); // use this func
    return true;
    }, array(    1, 2));
    ?>

    output:

    array(2) {
    [0] =>
    int(1)
    [1] =>
    int(2)
    }
    array(2) {
    [0] =>
    int(1)
    [1] =>
    int(2)
    }
    array(2) {
    [0] =>
    int(1)
    [1] =>
    int(2)
    }

    --------------------------------------------------
    or list each args:

    <?php
    $ai     = new ArrayIterator(range(0, 2));

    iterator_apply($ai, function($arg1, $arg2, $arg3) {
    var_dump([$arg1, $arg2, $arg3]);
    return     true;
    }, array(    1, 2));
    ?>

    same output.
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