Change array index by value and reorder

Question

I have an array of values, something like;

$array = array(1,2,3,4);

I want to be able to reposition an element and reorder.
Edit: To be clear on this point I don't just want to swop elements around, I want to move an element to a new place in the array and maintain the order of the other elements. For example;

// move value 3 to index[1], result
$array(1,3,2,4);
// or move value 1 to index[3], result
$array[2,3,4,1);

To make it clearer if required;

$array('alice','bob','colin','dave');
// move value 'colin' to index[1], result
$array('alice','colin','bob','dave');
// or move value 'alice' to index[3], result
$array('bob','colin','dave', 'alice');

Any ideas please.

Just to clarify: You want to take a value and move it to a specific index? — Josef Engelfrost
– Josef Engelfrost, Commented Feb 28, 2014 at 14:20
@JosefOttosson, yes. I would like to select what to move by its value if possible. — Rooneyl
– Rooneyl, Commented Feb 28, 2014 at 14:34
Maybe you could make this clearer by changing your example to include letters instead of numbers. All the replies so far take to indexes as arguments. Not that it's difficult to find the index of a value, but most answers miss that part of the question. Do you care about the value of the index? Are you interested only in numerical indexes? — Josef Engelfrost
– Josef Engelfrost, Commented Feb 28, 2014 at 14:43

Jack · Accepted Answer · 2014-02-28 14:17:01Z

1

This is copied from another StackOverflow thread by user hakre, but this function should work:

$array = array(1,2,3,4);
function moveElement(&$array, $a, $b) {
    $out = array_splice($array, $a, 1);
    array_splice($array, $b, 0, $out);
}

moveElement($array, 3, 1); // would move the value of the element at position [3] (the number 4 in the array example) to position [1]
//would output: Array ( [0] => 1 [1] => 4 [2] => 2 [3] => 3 )

It takes in the $array array and repositions element 3 to the position of [1] in the example. Use the function arguments to move whatever element value (in the example 3) to whatever position (in the example 1) you desire.

edited Feb 28, 2014 at 14:17

answered Feb 28, 2014 at 13:59

Jack

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6 Comments

Jack Over a year ago

Yes. Care to elaborate on your comment any?

putvande Over a year ago

This will result in 1, 4, 2, 3.

Jack Over a year ago

Thanks. I edited my post to reflect a '4' instead of the '3' I originally wrote by accident.

putvande Over a year ago

Yes, but OP wants 2,3,1,4

Benjamin Gruenbaum Over a year ago

Link to original source?

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ops · Accepted Answer · 2014-02-28 14:21:09Z

1

Try this code:

function swap_value(&$array,$first_index,$last_index){
    $save=$array[$first_index];
    $array[$first_index]=$array[$last_index];
    $array[$last_index]=$save;
    return $array;
}
$array = array(1,2,3,4); 
var_dump(swap_value($array,1,2));
var_dump(swap_value($array,0,2));

edited Feb 28, 2014 at 14:21

answered Feb 28, 2014 at 14:06

ops

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2 Comments

Alma Do Over a year ago

Will fail on associative arrays at least (because swapping values, not keys). Also keys would be untouched (so values will be swapped while keys will be not)

ops Over a year ago

@AlmaDo Ok.Changed function name to swap_value :-)

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