Non-destructive array extending in PHP

Created:25 May 2017 13:30:48 , in  Web development

Insert an item into an array without overwriting another item.

/*
  ArrayInsert::itemAt 
  Description: non-destructive extending of PHP number-indexed array
  Author: Sylwester Wojnowski
  WWW: wojnowski.net.pl

  paremeters:
    $arr - number-indexed Array
    $k - index to insert $item in $arr 
    $item - piece of data to be inserted in $arr 

  return value
    Extended array
*/
class ArrayInsert{
  public static function itemAt($arr,$k,$item){
    $j = 0;
    $n = count($arr);
    if($k >= $n){ 
      $arr[] = $item;
      return $arr;    
    }
    while( $j < $n ){
      if($j === $k){
        $i = -1;
        # items at the indices >= to $k have to be moved to the right 
        while($i + $n >= $j ){
         $arr[ $i + $n + 1 ] = $arr[$i + $n];
         if($i + $n === $j){
           $arr[$j] = $item;
           break;
         }
         $i--;
        }
      }
      $j++;
    }
    return $arr;
  }
}

Some calls below:

Inserting a string in the middle of array:

ArrayInsert::itemAt(array('a','c'),1,'b')
=> array('a','b','c')

Inserting an array in the middle of another array

ArrayInsert::itemAt(array('absinth','sake'),1,array('bitter ale','cask ale','mead'))
=> array('absinth',array('bitter ale','cask ale','mead'),'sake')

Inserting an object at the beginning of array:

$guitars = array(
  (object)array(
    'brand' => 'Jackson',
    'model' => 'King V' 
  ),
  (object)array(
    'brand' => 'Gibson',
    'model' => 'Les Paul Studio' 
  ),
  (object)array(
    'brand' => 'Schecter',
    'model' => 'Hellriser C1' 
  )
);
$bc_rich = (object)array('brand' => 'BC Rich', 'model' => 'Warlock');
$guitars = ArrayInsert::itemAt($guitars,0,$bc_rich); 

Guitars array has 4 items now, with the first items brand property value being "BC Rich".

Inserting NULL at a particular index.

ArrayInsert::itemAt(array('a',null),0,null)
=> array(null,'a',null)

Inserting multiple items in an array non-destructively

Now suppose you need to insert an array of items into your current array with first of the items to be put in at some particular index and the rest behind it.

One way to do that is by adding method "flatten" to ArrayInsert class. Here is a listing of this method:

public static function flatten($arr){
  return iterator_to_array(
    new RecursiveIteratorIterator(new RecursiveArrayIterator($arr))
  ,false);
}

And here is an example of use of "flatten" and "arrayAt" together:

# inserting an array of strings with the first of them being added at index 1
ArrayInsert::flatten(
  ArrayInsert::itemAt(array(),1,array('red','blue',array('orange','pink'),'green')))
);
=> array('red','blue','orange','pink','green')

This post was updated on 06 Oct 2021 21:28:56

Tags:  php