How to move an array value to the beginning of the array? [duplicate]

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);

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

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"
}

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;
}

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);
}

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]);

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

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

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

$b = array_reverse( $a );

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

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 ) 

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);

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);