PHP Cookbook

4.7. Appending One Array to Another

Problem

You want to combine two arrays into one.

Solution

Use array_merge( ):

$garden = array_merge($fruits, $vegetables);

Discussion

The array_merge( ) function works with both predefined arrays and arrays defined in place using array( ):

$p_languages = array('Perl', 'PHP');
$p_languages = array_merge($p_languages, array('Python'));
print_r($p_languages);
Array
               (
                   [0] => PHP
                   [1] => Perl
                   [2] => Python
               )

Accordingly, merged arrays can be either preexisting arrays, as with $p_languages, or anonymous arrays, as with array('Python').

You can’t use array_push( ) , because PHP won’t automatically flatten out the array into series of independent variables, and you’ll end up with a nested array. Thus:

array_push($p_languages, array('Python'));
print_r($p_languages);
Array
               (
                   [0] => PHP
                   [1] => Perl
                   [2] => Array
                       (
                           [0] => Python
                       )

               )

Merging arrays with only numerical keys causes the arrays to get renumbered, so values aren’t lost. Merging arrays with string keys causes the second array to overwrite the value of any duplicated keys. Arrays with both types of keys exhibit both types of behavior. For example:

$lc = array('a', 'b' => 'b'); // lower-case letters as values
$uc = array('A', 'b' => 'B'); // upper-case letters as values
$ac = array_merge($lc, $uc);  // all-cases?
print_r($ac);
Array
               (
                   [0] => a
                   [b] => B
                   [1] => A
               )

The uppercase A has been renumbered from index 0 to index 1, to avoid a collision, and merged onto the end. The uppercase B has overwritten ...