How to insert element into array to specific position?

Question

Hello,

Let's imagine that we have two arrays

$array_1 = array(
  '0' => 'zero',
  '1' => 'one',
  '2' => 'two',
  '3' => 'three',
);

$array_2 = array(
  'zero'  => '0',
  'one'   => '1',
  'two'   => '2',
  'three' => '3',
);

Now, I'd like to insert array('sample_key' => 'sample_value') after third element of each array. How can I do it?

Thank you.

Answer 1

Hi,

Have a look at those slides there are many examples:

http://www.benoist.ch/coursWebProgramming/slides/base/slides-beamer.pdf

have also a look at those source code examples:

http://www.benoist.ch/coursWebProgramming/examples/basic-examples.php

cheers

Daniel

Answer 2

In the context of an associative array ($array_2) positioning within the array doesn't make a difference. You'd just add:

$array_2['sample_key'] = 'sample_value';

In a standard array with numbered keys (which is what $array_1 appears to be), you'd do a similar thing:

$array_1[3] = 'sample_value';

Remember, array numbering starts at 0, so position "3" is really the fourth element of the array. This would overwrite whatever you already had listed in position 3, though.

Answer 3

function array_insert($arr, $insert, $position) {
    foreach ($arr as $key => $value) {
            if ($i == $position) {
                    foreach ($insert as $ikey => $ivalue) {
                            $ret[$ikey] = $ivalue;
                    }
            }
            $ret[$key] = $value;
            $i++;
    }
    return $ret;
}

doesn't really look handy, but it works.

Answer 4

For your first array, use splice:

$array_1 = array(
  '0' => 'zero',
  '1' => 'one',
  '2' => 'two',
  '3' => 'three',
);

array_splice($array_1, 3, 0, 'more');
print_r($array_1);

output:

Array(
    [0] => zero
    [1] => one
    [2] => two
    [3] => more
    [4] => three
)

for the second one there is no order so you just have to do :

$array_2['more'] = '2.5';
print_r($array_2);

And sort the keys by whatever you want.

Answer 5

I recently wrote a function to do something similar to what it sounds like you're attempting, it's a similar approach to clasvdb's answer.

function magic_insert($index,$value,$input_array ) {
  if (isset($input_array[$index])) {
    $output_array = array($index=>$value);
    foreach($input_array as $k=>$v) {
      if ($k<$index) {
        $output_array[$k] = $v;
      } else {
        if (isset($output_array[$k]) ) {
          $output_array[$k+1] = $v;
        } else {
          $output_array[$k] = $v;
        }
      } 
    }

  } else {
    $output_array = $input_array;
    $output_array[$index] = $value;
  }
  ksort($output_array);
  return $output_array;
}

Basically it inserts at a specific point, but avoids overwriting by shifting all items down.

Answer 6

$res = array_slice($array, 0, 3, true) +
    array("my_key" => "my_value") +
    array_slice($array, 3, count($array)-3, true);

This example:

$array = array(
  'zero'  => '0',
  'one'   => '1',
  'two'   => '2',
  'three' => '3',
);
$res = array_slice($array, 0, 3, true) +
    array("my_key" => "my_value") +
    array_slice($array, 3, count($array) - 1, true) ;
print_r($res);

gives:

Array
(
    [zero] => 0
    [one] => 1
    [two] => 2
    [my_key] => my_value
    [three] => 3
)