How to add an array value to the middle of an associative array?

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

Try this

$array['c']=3;

An associative array is not ordered by default, but if you wanted to sort them alphabetically you could use ksort() to sort the array by it's key.

If you check out the PHP article for ksort() you will se it's easy to sort an array by its key, for example:

<?php
$fruits = array("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");
ksort($fruits);
foreach ($fruits as $key => $val) {
    echo "$key = $val\n";
}
?>

// The above example will output:
a = orange
b = banana
c = apple
d = lemon

Answer 2

Associative arrays are not ordered, so you can simply add with $array['c'] = 3.

If order is important, one option is switch to a data structure more like:

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

Then, use array_splice($array, 2, 0, array('c' => 3)) to insert at position 2. See manual on array_splice.

Answer 3

An associative array is made by hashing the key and so are not ordered as you think with an alphabetical order, or numerical order but only with the result of the hashing function

Answer 4

you can add it by doing

$array['c']=3;

and if you absolutely want it sorted for printing purposes, you can use php's ksort($array) function

if the keys are not sortable by ksort, then you will have to create your own sort by using php's uasort function. see examples here

http://php.net/manual/en/function.uasort.php

Answer 5

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 6

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 7

function insertValue($oldArray, $newKey, $newValue, $followingKey) {

    $newArray = array ();
    foreach (array_keys($oldArray) as $k) {
        if ($k == $followingKey)
            $newArray[$newKey] = $newValue;
        $newArray[$k] = $oldArray [$k];
    }

    return $newArray;
}

You call it as

insertValue($array, 'c', '3', 'z')

As for Edit 5:

edit your sql, so that it reads

SELECT ..., pizza, drink, pizza+drink as full_meal, ... FROM ....

and you have the column automagically:

Array (
  ...
  'pizza' => 12,
  'drink' => 5,
  'full_meal' => 17,
  ...
)

Answer 8

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];
    }
}