15

I want to call a function on each element in an array. This is obviously very easy with a foreach(), but where I start breaking down is when arrays contain arrays. Can someone help me out with a function that will execute some code for every key -> value pair from a set of arrays within arrays. The depth could, in theory, be infinite, but a good limit would be 3 iterations (array in array in array) if recursion couldn't work.

An example array would be one taken from $_POST below:

Array
(
    [languages] => Array
    (
        [0] => php
        [1] => mysql
        [2] => inglip
    )

    [rates] => Array
    (
        [incall] => Array
        (
            [1hr] => 10
        )

        [outcall] => Array
        (
            [1hr] => 10
        )

    )
)

Just to make sure, what I want to do is run a piece of code (a function) that is passed every 'end node' in the array structure, so in the example above, it would be called when...

[0] => php
[1] => mysql
[2] => inglip
[1hr] => 10
[1hr] => 10

... is found.

Thanks for any help,

James

Improve this question
3
  • 6
    (sidenote) The correct term for "end node" is leaf. Commented Apr 2, 2011 at 16:16
  • also see Get All Values in One Array. It's not strictly a duplicate, but highly related. Commented Apr 2, 2011 at 17:05
  • 1
    Also have a look at bool array_walk_recursive( ... ) => php.net/manual/en/function.array-walk-recursive.php Commented Sep 16, 2015 at 12:48

9 Answers 9

Reset to default
26

That's a perfect job for Iterators:

$iterator = new RecursiveIteratorIterator(new RecursiveArrayIterator($array));
foreach($iterator as $key => $value) {
    echo "$key => $value\n";
}

See Introduction to SPL Iterators and Live Demo on codepad

EDIT: the alternative would be array_walk_recursive as show in Finbarr's answer below

Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

11

See array_walk_recursive - a PHP library function that recursively calls a user defined function against a provided array.

From PHP docs:

<?php
$sweet = array('a' => 'apple', 'b' => 'banana');
$fruits = array('sweet' => $sweet, 'sour' => 'lemon');

function test_print($item, $key)
{
    echo "$key holds $item\n";
}

array_walk_recursive($fruits, 'test_print');
?>

Output:

a holds apple
b holds banana
sour holds lemon

Note that Any key that holds an array will not be passed to the function..

EDIT: slightly less ugly example:

<?php
$sweet = array('a' => 'apple', 'b' => 'banana');
$fruits = array('sweet' => $sweet, 'sour' => 'lemon');
array_walk_recursive($fruits, function ($item, $key) {
    echo "$key holds $item\n";
});
?>
Improve this answer

5 Comments

+1 Next to my own answer this is the only practical approach to the problem. All those userland recursive functions are just ridiculous. You might want to add a small usage example though to illustrate usage.
@Jam array_walk_recursive perfectly fits "call a function on each element in an array" though. but okay, I wont complain about an accepted answer :) Will edit mine to include a link here though. Thanks!
No complaints from this end. They were both perfectly valid answers. There are many ways to solve the same problem, and it is down to the programmer to choose whatever way suits them.
The only slight niggle I have with this answer is having to reference the function name as a string. To me, it's cleaner to use the RecursiveIterator function.
Well, as with all PHP library functions that are designed to callback you could pass an anonymous function directly to array_walk_recursive - you need not use the function name as string.
7

Typically, in this kind of situation, you'll have to write a recursive function -- which will deal with an item if it's not an array ; and call itself on an item if it's an array.


Here, you could have something like this :

$arr = array(
    'languages' => array(
        'php', 'mysql', 'inglip', 
    ), 
    'rates' => array(
        'incall' => array('1hr' => 10), 
        'outcall' => array('1hr' => 10), 
    ), 
);

function recurse($item) {
    foreach ($item as $key => $value) {
        if (is_array($value)) {
            recurse($value);
        } else {
            echo "$key : $value\n";
        }
    }
}


And calling this recursive function on your array :

recurse($arr);

Would get you :

0 : php
1 : mysql
2 : inglip
1hr : 10
1hr : 10
Improve this answer

Comments

3

Here's a simple reusable implementation:

function recursive_foreach($array, $callback) {
    foreach($array as $key => $value) {
        if (is_array($value)) {
            recursive_foreach($value, $callback);
        }
        else {
            call_user_func($callback, $key, $value);
        }
    }
}

Where $callback is a callback accepting two arguments: key and value. For example:

recursive_foreach($array, function($k, $v) {
    echo "$k => $v<br>";
});
Improve this answer

2 Comments

Did not know that PHP supported anonymous functions!
@Finbarr @Jon PHP supported anonymous functions before 5.3, too with the create_function function. It's just awkward to use and slow.
1

I want to call a function on each element in an array. This is obviously very easy with a foreach()

If you want to run a function on every element of a deep array, you can use array_walk_recursive()

array_walk_recursive($array, function($v, $k)
{  
    echo "$k => $v\n";
});

If you want to iterate over each element with foreach, you need a recursive iterator as mentionned previously.

If you're not sure which one to use, go with foreach + recursive iterator. It's easier to grasp for most people.

Improve this answer

Comments

1 
function getEndNodes($input, $ret = array()) {

    foreach ($input as $key => $value) {
        if (!is_array($input[$key])) {
            $ret[$key] = $value;
        } else {
            $ret = getEndNodes($input[$key],$ret);
        }
    }

    return $ret;

}


// Usage: 
$endNodes = getEndNodes($yourarray);
Improve this answer

Comments

0 
function array_spelunk($array = array()) {
    foreach($array as $key => $node) {
        if (is_array($node)) {
            array_spelunk($node);
        } else {
           echo "[$key] [$node]\n";
        }
    }
}

array_spelunk($your_nested_array);
Improve this answer

Comments

0 
function recurse($element, $key = null) {
  if(is_array($element)) {
    foreach($element as $k => $v) {
      recurse($v, $k);
    }
  }else{
    //Do what you want here. $element is value, $key is the key
  } 
}
Improve this answer

Comments

0 
function traverseArray($array)
{ 
    foreach($array as $key=>$value)
    { 
        if(is_array($value))
        { 
            traverseArray($value); 
        }else{
            echo '['.$key.']'.' => '.$value.'<br />\n'; 
        } 
    }
}
Improve this answer

1 Comment

Yeah this is the first thing I came up with. Thanks for the effort in posting your answer, but it's not an ideal solution to say the least.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.