php associative array key order (not sort)

Question

My array:

$data = array('two' => 2, 'one' => 1, 'three' => 3);

Now, with when I iterate the array, the first value that will come up will probably be

$data['two'] // = 2 @ index[0]

right?

What if I want to move the $data[1] to the position of $data[0] ?

To rephrase:

How do I make the array look like this (so that 'one' comes up at $data[0])

$data = array('one' => 1, 'two' => 2, 'three' => 3

Why do I need this?

I use code igniter, the table->generate built-in function takes an assoc array and creates a table but offers no method of arranging the columns. This is why I would like to move the columns in the source array.

Solution 1

Take a look at daniele centamore's comment on PHP's array_splice() function, where he provides a couple of functions for moving the elements in an non-associative array.

<?php

// $input  (Array) - the array containing the element
// $index (int) - the index of the element you need to move

function moveUp($input,$index) {
      $new_array = $input;

       if((count($new_array)>$index) && ($index>0)){
                 array_splice($new_array, $index-1, 0, $input[$index]);
                 array_splice($new_array, $index+1, 1);
             } 

       return $new_array;
}

function moveDown($input,$index) {
       $new_array = $input;

       if(count($new_array)>$index) {
                 array_splice($new_array, $index+2, 0, $input[$index]);
                 array_splice($new_array, $index, 1);
             } 

       return $new_array;
}  

$input = array("red", "green", "blue", "yellow");

$newinput = moveUp($input, 2);
// $newinput is array("red", "blue", "green", "yellow")

$input = moveDown($newinput, 1);
// $input is array("red", "green", "blue", "yellow")

?>

Solution 2

Two possible solutions (without using array_splice):

1) Create a new array with the new order of the keys.

$new_keys = array('one', 'two', 'three');
$new_data = array();
foreach ($new_keys as $key) {
    $new_data[$key] = $data[$key];
}
$data = $new_data;

2) Move the element one upfront, remove it from $data and copy the rest of the array.

function rearrangeData($data) {
    $result['one'] = $data['one'];
    unset($data['one']);
    return array_merge($result, $data);
}    
$data = rearrangeData($data);

Solution 3

See ksort and uksort.

Here's a working example:

<?php

$data = array('two' => 2, 'one' => 1, 'three' => 3);
print_r($data);
ksort($data);
echo "ksort:\n";
print_r($data);
uksort($data,'cmp');
echo "uksort:\n";
print_r($data);
function cmp($a, $b)
{
    $num=' one two three four five six seven eight nine ten';
    $ai = stripos($num,$a);
    $bi = stripos($num,$b);
    if ($ai>0 && $bi>0) {
        return ($ai > $bi) ? 1 : -1;
    }
    return strcasecmp($a, $b);
}

Output:

Array
(
    [two] => 2
    [one] => 1
    [three] => 3
)
ksort:
Array
(
    [one] => 1
    [three] => 3
    [two] => 2
)
uksort:
Array
(
    [one] => 1
    [two] => 2
    [three] => 3
)

Run this: http://codepad.org/yAK1b1IP

Solution 4

PHP has 13 functions for sorting arrays, by key, by value, by user-defined functions where you can specify that "one" comes before "two". There's also array_shift, array_unshift, array_push and array_pop for moving things onto or off the front or end of the array. You can build a whole new array from the existing one.

View more solutions

Comments

[nizzle]

I know, these functions are great. However, notice how it says 'Not sort' in the title. Also, I couldn't find the function array_move_index('one',0);

[Dan Grossman]

Rearranging a set of items is sorting. Just because your ordering is not lexicographic or numeric doesn't mean arranging arrays in that order isn't sorting. That's the very meaning of the word.

[ioleo]

Exacly, you should use usort and write a simple closure.

[Ben]

That doesn't really answer the question. Daniele's example is not for associative arrays

[oriadam]

This does not sort by key, it sorts by value! See here: codepad.org/wUAsV5hr

[MLK.DEV]

Question specifically requested a non-sort solution.

[Sebastian]

Thank you! One suggestion to solution 1: If you have more keys as $new_keys have, it will strip the others completely. Maybe there should be a fallback and let the others "unsorted".