PHP foreach() with arrays within arrays?

问题:

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

回答1:

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

回答2:

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";
});
?>

回答3:

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

回答4:

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>";
});

回答5:

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);

回答6:

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.

回答7:

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
  } 
}

回答8:

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

回答9:

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);