CODEWITHSUNDEEP
phparrayssorting
Jarred
Jarred

Reputation: 219

How to move an array value to the beginning of the array?

I have a PHP array similar to this:

0 => "red",
1 => "green",
2 => "blue",
3 => "yellow"

I want to move yellow to index 0.

How do I move any one of these elements to the beginning? How would I move green to index 0, or blue to index 0? This question is not exclusively about moving the last element to the beginning.

Upvotes: 21

Views: 29106

Answers (11)

Peter Bailey
Peter Bailey

Reputation: 105914

This function does satisfy that request

/**
 * Move array element by index.  Only works with zero-based,
 * contiguously-indexed arrays
 *
 * @param array $array
 * @param integer $from Use NULL when you want to move the last element
 * @param integer $to   New index for moved element. Use NULL to push
 * 
 * @throws Exception
 * 
 * @return array Newly re-ordered array
 */
function moveValueByIndex( array $array, $from=null, $to=null )
{
  if ( null === $from )
  {
    $from = count( $array ) - 1;
  }

  if ( !isset( $array[$from] ) )
  {
    throw new Exception( "Offset $from does not exist" );
  }

  if ( array_keys( $array ) != range( 0, count( $array ) - 1 ) )
  {
    throw new Exception( "Invalid array keys" );
  }

  $value = $array[$from];
  unset( $array[$from] );

  if ( null === $to )
  {
    array_push( $array, $value );
  } else {
    $tail = array_splice( $array, $to );
    array_push( $array, $value );
    $array = array_merge( $array, $tail );
  }

  return $array;
}

And, in usage

$arr = array( 'red', 'green', 'blue', 'yellow' );

echo implode( ',', $arr ); // red,green,blue,yellow

// Move 'blue' to the beginning
$arr = moveValueByIndex( $arr, 2, 0 );

echo implode( ',', $arr ); // blue,red,green,yellow

Upvotes: 14

madhukar
madhukar

Reputation: 61

Here is an alternate way.

$colors = array("red","green","blue","yellow");
$color_to_move = ["yellow"];
$colors_wo_yellow = array_diff($colors, $color_to_move);// This will give an array without "yellow"
//Now add "yellow" as 1st element to $
array_unshift($colors_wo_yellow,$color_to_move[0]);

Upvotes: 3

Eugene Kaurov
Eugene Kaurov

Reputation: 2991

PHP: move any element to the first or any position:

$sourceArray = array(
    0 => "red",
    1 => "green",
    2 => "blue",
    3 => "yellow"
);
// set new order
$orderArray = array(
    3 => '',
    1 => '',
);
$result = array_replace($orderArray, $sourceArray);
print_r($result);

Upvotes: 0

James Alday
James Alday

Reputation: 871

This is very similar to SharpC's answer but accounts for the fact that you may not know where the value is in the array (it's key) or if it is even set. The 'if' check will skip over it if the color isn't set or if it's already the first element in the array.

$color = 'yellow';
$color_array = array("red", "green", "blue", "yellow");

$key = array_search($color, $color_array);

if ($key > 0) {
   unset($color_array[$key]);
   array_unshift($color_array, $color);
}

Upvotes: 4

dylan maxey
dylan maxey

Reputation: 67

If you aren't always planning on bringing the very last object to the beginning of the array, this would be the most simplistic way to go about it...

$array = array('red','green','blue','yellow');
unset($array[array_search($searchValue, $array)]);
array_unshift($array, $searchValue);

Upvotes: 0

SharpC
SharpC

Reputation: 7474

This seems like the simplest way to me. You can move any position to the beginning, not just the last (in this example it moves blue to the beginning).

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

$movecolour = $colours[2];
unset($colours[2]);
array_unshift($colours, $movecolour);

Upvotes: 31

dstonek
dstonek

Reputation: 975

You want to move one of the elements to the beginning. Let's say

$old = array(
'key1' =>'value1', 
'key2' =>'value2', 
'key3' =>'value3', 
'key4' =>'value4');

And you want to move key3 to the beginnig.

$new = array();
$new['key3'] = $old['key3']; // This is the first item of array $new
foreach($old as $key => $value) // This will continue adding $old values but key3
{
if($key != 'key3')$new[$key]=$value;
}

Upvotes: 5

Dereleased
Dereleased

Reputation: 10087

This function will allow you to move an element to an arbitrary position within the array, while leaving the rest of the array untouched:

function array_reorder($array, $oldIndex, $newIndex) {
    array_splice(
        $array,
        $newIndex,
        count($array),
        array_merge(
            array_splice($array, $oldIndex, 1),
            array_slice($array, $newIndex, count($array))
        )
    );
    return $array;
}

Hopefully the usage is fairly obvious, so this:

$array = array('red','green','blue','yellow',);

var_dump(
    array_reorder($array, 3, 0),
    array_reorder($array, 0, 3),
    array_reorder($array, 1, 3),
    array_reorder($array, 2, 0)
);

Will output this:

array(4) {
  [0]=>
  string(6) "yellow"
  [1]=>
  string(3) "red"
  [2]=>
  string(5) "green"
  [3]=>
  string(4) "blue"
}
array(4) {
  [0]=>
  string(5) "green"
  [1]=>
  string(4) "blue"
  [2]=>
  string(6) "yellow"
  [3]=>
  string(3) "red"
}
array(4) {
  [0]=>
  string(3) "red"
  [1]=>
  string(4) "blue"
  [2]=>
  string(6) "yellow"
  [3]=>
  string(5) "green"
}
array(4) {
  [0]=>
  string(4) "blue"
  [1]=>
  string(3) "red"
  [2]=>
  string(5) "green"
  [3]=>
  string(6) "yellow"
}

Upvotes: 9

Sarfraz
Sarfraz

Reputation: 382881

You can do like this:

$array = array("red", "green", "blue", "yellow");
$last = array_pop($array);
array_unshift($array, $last);
print_r($array);

Result:

Array ( [0] => yellow [1] => red [2] => green [3] => blue )

Upvotes: 0

Cups
Cups

Reputation: 6896

$a = array('red','green', 'blue','yellow');

$b = array_reverse( $a );

If your question is how to make the last become the first.

Upvotes: 0

ceejayoz
ceejayoz

Reputation: 180167

$array = array(
  'red',
  'green',
  'blue',
  'yellow',
);

$last = array_pop($array);
array_unshift($array, $last);

Upvotes: 0

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