How to add an array value to the middle of an asso

Question

Lets say I have this array:

$array = array('a'=>1,'z'=>2,'d'=>4);

Later in the script, I want to add the value 'c'=>3 before 'z'. How can I do this?

EDIT: Yes, the order is important. When I run a foreach() through the array, I do NOT want this newly added value added to the end of the array. I am getting this array from a mysql_fetch_assoc()

EDIT 2: The keys I used above are placeholders. Using ksort() will not achieve what I want.

EDIT 3: http://www.php.net/manual/en/function.array-splice.php#88896 accomplishes what I'm looking for but I'm looking for something simpler.

EDIT 4: Thanks for the downvotes. I gave feedback to your answers and you couldn't help, so you downvoted and requested to close the question because you didn't know the answer. Thanks.

EDIT 5: Take a sample db table with about 30 columns. I get this data using mysql_fetch_assoc(). In this new array, after column 'pizza' and 'drink', I want to add a new column 'full_dinner' that combines the values of 'pizza' and 'drink' so that when I run a foreach() on the said array, 'full_dinner' comes directly after 'drink'

Answer 1

An alternative approach is to supplement the associative array structure with an ordered index that determines the iterative order of keys. For instance:

$index = array('a','b','d');

// Add new value and update index
$array['c'] = 3;
array_splice($index, 2, 0, 'c');

// Iterate the array in order
foreach $index as $key {
   $value = $array[$key];
}

Answer 2

A simple approach to this is to iterate through the original array, constructing a new one as you go:

function InsertBeforeKey( $originalArray, $originalKey, $insertKey, $insertValue ) {

    $newArray = array();
    $inserted = false;

    foreach( $originalArray as $key => $value ) {

        if( !$inserted && $key === $originalKey ) {
            $newArray[ $insertKey ] = $insertValue;
            $inserted = true;
        }

        $newArray[ $key ] = $value;

    }

    return $newArray;

}

Then simply call

$array = InsertBeforeKey( $array, 'd', 'c', 3 );

Answer 3

For the moment the best i can found to try to minimize the creation of new arrays are these two functions :

the first one try to replace value into the original array and the second one return a new array.

// replace value into the original array
function insert_key_before_inplace(&$base, $beforeKey, $newKey, $value) {
 $index = 0;
 foreach($base as $key => $val) {
    if ($key==$beforeKey) break;
    $index++;
 }
 $end = array_splice($base, $index, count($base)-$index);
 $base[$newKey] = $value;
 foreach($end as $key => $val) $base[$key] = $val;
}


$array = array('a'=>1,'z'=>2,'d'=>4);

insert_key_before_inplace($array, 'z', 'c', 3);

var_export($array); // array ( 'a' => 1, 'c' => 3, 'z' => 2, 'd' => 4, )

---

// create new array
function insert_key_before($base, $beforeKey, $newKey, $value) {
 $index = 0;
 foreach($base as $key => $val) {
    if ($key==$beforeKey) break;
    $index++;
 }
 $end = array_splice($base, $index, count($base)-$index);
 $base[$newKey] = $value;
 return $base+$end;
}


$array = array('a'=>1,'z'=>2,'d'=>4);

$newArray=insert_key_before($array, 'z', 'c', 3);

var_export($array); // ( 'a' => 1, 'z' => 2, 'd' => 4, )

var_export($newArray); // array ( 'a' => 1, 'c' => 3, 'z' => 2, 'd' => 4, )

Answer 4

You can define your own sortmap when doing a bubble-sort by key. It's probably not terribly efficient but it works.

<pre>
<?php

$array = array('a'=>1,'z'=>2,'d'=>4);

$array['c'] = 3;

print_r( $array );

uksort( $array, 'sorter' );

print_r( $array );

function sorter( $a, $b )
{
    static $ordinality = array(
        'a' => 1
      , 'c' => 2
      , 'z' => 3
      , 'd' => 4
    );
    return $ordinality[$a] - $ordinality[$b];
}

?>
</pre>

Here's an approach based on ArrayObject using this same concept

$array = new CitizenArray( array('a'=>1,'z'=>2,'d'=>4) );
$array['c'] = 3;

foreach ( $array as $key => $value )
{
    echo "$key: $value <br>";
}

class CitizenArray extends ArrayObject
{
    static protected $ordinality = array(
        'a' => 1
      , 'c' => 2
      , 'z' => 3
      , 'd' => 4
    );

    function offsetSet( $key, $value )
    {
        parent::offsetSet( $key, $value );
        $this->uksort( array( $this, 'sorter' ) );
    }

    function sorter( $a, $b )
    {
        return self::$ordinality[$a] - self::$ordinality[$b];
    }
}

Answer 5

Great usage of array functions but how about this as a simpler way:

Add a static column to the SQL and then replace it in the resultant array. Order stays the same:

SQL :

Select pizza , drink , 'pizza-drink' as 'pizza-drink' , 28 columns..... From Table

Array :

$result['pizza-drink'] = $result['pizza'] . $result['drink'];

Answer 6

Am I missing something?

$key = 'z';
$offset = array_search($key, array_keys($array));

$result = array_merge
        (
            array_slice($array, 0, $offset),
            array('c' => 3),
            array_slice($array, $offset, null)
        );

---

Handling of nonexistent keys (appending $data by default):

function insertBeforeKey($array, $key, $data = null)
{
    if (($offset = array_search($key, array_keys($array))) === false) // if the key doesn't exist
    {
        $offset = 0; // should we prepend $array with $data?
        $offset = count($array); // or should we append $array with $data? lets pick this one...
    }

    return array_merge(array_slice($array, 0, $offset), (array) $data, array_slice($array, $offset));
}

Demo:

$array = array('a' => 1, 'z' => 2, 'd' => 4);

// array(4) { ["a"]=> int(1) ["c"]=> int(3) ["z"]=> int(2) ["d"]=> int(4) }
var_dump(insertBeforeKey($array, 'z', array('c' => 3)));

// array(4) { ["a"]=> int(1) ["z"]=> int(2) ["d"]=> int(4) ["c"]=> int(3) }
var_dump(insertBeforeKey($array, 'y', array('c' => 3)));