PHP Merge or concatenate arrays


Example

$fruit1 = ['apples', 'pears'];
$fruit2 = ['bananas', 'oranges'];

$all_of_fruits = array_merge($fruit1, $fruit2);
// now value of $all_of_fruits is [0 => 'apples', 1 => 'pears', 2 => 'bananas', 3 => 'oranges']

Note that array_merge will change numeric indexes, but overwrite string indexes

$fruit1 = ['one' => 'apples',  'two' => 'pears'];
$fruit2 = ['one' => 'bananas', 'two' => 'oranges'];

$all_of_fruits = array_merge($fruit1, $fruit2);
// now value of $all_of_fruits is ['one' => 'bananas', 'two' => 'oranges']

array_merge overwrites the values of the first array with the values of the second array, if it cannot renumber the index.

You can use the + operator to merge two arrays in a way that the values of the first array never get overwritten, but it does not renumber numeric indexes, so you lose values of arrays that have an index that is also used in the first array.

$fruit1 = ['one' => 'apples',  'two' => 'pears'];
$fruit2 = ['one' => 'bananas', 'two' => 'oranges'];

$all_of_fruits = $fruit1 + $fruit2;
// now value of $all_of_fruits is ['one' => 'apples', 'two' => 'pears']

$fruit1 = ['apples', 'pears'];
$fruit2 = ['bananas', 'oranges'];

$all_of_fruits = $fruit1 + $fruit2;
// now value of $all_of_fruits is [0 => 'apples', 1 => 'pears']