array_merge

(PHP 4, PHP 5, PHP 7, PHP 8)

array_merge — Fusionne plusieurs tableaux en un seul

Description

array_merge(array ...$arrays): array

array_merge() rassemble les éléments d'un ou de plusieurs tableaux en ajoutant les valeurs de l'un à la fin de l'autre. Le résultat est un tableau.

Si les tableaux d'entrées ont des clés en commun, alors, la valeur finale pour cette clé écrasera la précédente. Cependant, si les tableaux contiennent des clés numériques, la valeur finale n'écrasera pas la valeur originale, mais sera ajoutée.

Les clés numériques des tableaux d'entrées seront renumérotées en clés incrémentées partant de zéro dans le tableau fusionné.

Liste de paramètres

arrays: Liste de tableaux variable à fusionner.

Valeurs de retour

Retourne le tableau résultant. Si appellé sans arguments, retourne un tableau vide.

Historique

Version	Description
7.4.0	Cette fonction peut désormais être appelée sans paramètres. Auparavant, au moins un paramètre était requis.

Exemples

Exemple #1 Exemple avec array_merge()

<?php
$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_merge($array1, $array2);
print_r($result);
?>

L'exemple ci-dessus va afficher :

Array
(
    [color] => green
    [0] => 2
    [1] => 4
    [2] => a
    [3] => b
    [shape] => trapezoid
    [4] => 4
)

Exemple #2 Exemple simple avec array_merge()

<?php
$array1 = array();
$array2 = array(1 => "data");
$result = array_merge($array1, $array2);
?>

N'oubliez pas que les index numériques seront réindexés !

Array
(
    [0] => data
)

Si vous voulez ajouter des éléments du second tableau au premier sans pour autant écraser ou ré-indexer les éléments du premier, utilisez l'opérateur d'union + :

<?php
$array1 = array(0 => 'zero_a', 2 => 'two_a', 3 => 'three_a');
$array2 = array(1 => 'one_b', 3 => 'three_b', 4 => 'four_b');
$result = $array1 + $array2;
var_dump($result);
?>

Les clés du premier tableau sont préservées. Si une clé existe dans les 2 tableaux, alors l'élément du premier sera utilisé et la clé correspondante du second sera ignorée.

array(5) {
  [0]=>
  string(6) "zero_a"
  [2]=>
  string(5) "two_a"
  [3]=>
  string(7) "three_a"
  [1]=>
  string(5) "one_b"
  [4]=>
  string(6) "four_b"
}

Exemple #3 Exemple avec array_merge() avec des types non-tableaux

<?php
$beginning = 'foo';
$end = array(1 => 'bar');
$result = array_merge((array)$beginning, (array)$end);
print_r($result);
?>

L'exemple ci-dessus va afficher :

    Array
    (
        [0] => foo
        [1] => bar
    )

Voir aussi

array_merge_recursive() - Combine un ou plusieurs tableaux ensemble, récursivement
array_replace() - Remplace les éléments d'un tableau par ceux d'autres tableaux
array_combine() - Crée un tableau à partir de deux autres tableaux
les opérateurs de tableau

＋add a note

User Contributed Notes 8 notes

down

303

Julian Egelstaff ¶

14 years ago

In some situations, the union operator ( + ) might be more useful to you than array_merge.  The array_merge function does not preserve numeric key values.  If you need to preserve the numeric keys, then using + will do that.

ie:

<?php

$array1[0] = "zero";
$array1[1] = "one";

$array2[1] = "one";
$array2[2] = "two";
$array2[3] = "three";

$array3 = $array1 + $array2;

//This will result in::

$array3 = array(0=>"zero", 1=>"one", 2=>"two", 3=>"three");

?>

Note the implicit "array_unique" that gets applied as well.  In some situations where your numeric keys matter, this behaviour could be useful, and better than array_merge.

--Julian

down

ChrisM ¶

1 year ago

I wished to point out that while other comments state that the spread operator should be faster than array_merge, I have actually found the opposite to be true for normal arrays. This is the case in both PHP 7.4 as well as PHP 8.0. The difference should be negligible for most applications, but I wanted to point this out for accuracy.

Below is the code used to test, along with the results:

<?php
$before = microtime(true);

for ($i=0 ; $i<10000000 ; $i++) {
    $array1 = ['apple','orange','banana'];
    $array2 = ['carrot','lettuce','broccoli'];
    
    $array1 = [...$array1,...$array2];
}

$after = microtime(true);
echo ($after-$before) . " sec for spread\n";

$before = microtime(true);

for ($i=0 ; $i<10000000 ; $i++) {
    $array1 = ['apple','orange','banana'];
    $array2 = ['carrot','lettuce','broccoli'];
    
    $array1 = array_merge($array1,$array2);
}

$after = microtime(true);
echo ($after-$before) . " sec for array_merge\n";
?>

PHP 7.4:
1.2135608196259 sec for spread
1.1402177810669 sec for array_merge

PHP 8.0:
1.1952061653137 sec for spread
1.099925994873 sec for array_merge

down

Andreas Hofmann ¶

2 years ago

In addition to the text and Julian Egelstaffs comment regarding to keep the keys preserved with the + operator:
When they say "input arrays with numeric keys will be renumbered" they MEAN it. If you think you are smart and put your numbered keys into strings, this won't help. Strings which contain an integer will also be renumbered! I fell into this trap while merging two arrays with book ISBNs as keys. So let's have this example:

<?php
    $test1['24'] = 'Mary';
    $test1['17'] = 'John';

    $test2['67'] = 'Phil';
    $test2['33'] = 'Brandon';

    $result1 = array_merge($test1, $test2);
    var_dump($result1);

    $result2 = [...$test1, ...$test2];    // mentioned by fsb
    var_dump($result2);
?>

You will get both:

array(4) {
  [0]=>
  string(4) "Mary"
  [1]=>
  string(4) "John"
  [2]=>
  string(4) "Phil"
  [3]=>
  string(7) "Brandon"
}

Use the + operator or array_replace, this will preserve - somewhat - the keys:

<?php
    $result1 = array_replace($test1, $test2);
    var_dump($result1);

    $result2 = $test1 + $test2;
    var_dump($result2);
?>

You will get both:

array(4) {
  [24]=>
  string(4) "Mary"
  [17]=>
  string(4) "John"
  [67]=>
  string(4) "Phil"
  [33]=>
  string(7) "Brandon"
}

The keys will keep the same, the order will keep the same, but with a little caveat: The keys will be converted to integers.

down

fsb at thefsb dot org ¶

3 years ago

We no longer need array_merge() as of PHP 7.4.

    [...$a, ...$b]

does the same as

    array_merge($a, $b)

and can be faster too.

https://wiki.php.net/rfc/spread_operator_for_array#advantages_over_array_merge

down

JoshE ¶

1 year ago

Not to contradict ChrisM's test, but I ran their code example and I got very different results for PHP 8.0.

Testing PHP 8.0.14
1.4955070018768 sec for spread
4.4120140075684 sec for array_merge

down

-1

Hayley Watson ¶

8 months ago

Using the spread operator with array_merge allows merging any number of arrays together in one operation:

<?php
array_merge(...$array_of_arrays);
?>

Perhaps $array_of_arrays was built up in a loop, with $array_of_arrays[] = $another_array inside the loop. Collecting the arrays together this way and then merging them all at once is many times faster than repeatedly merging arrays two at a time (doing array_merge inside the loop).

down

-1

gwyneth dot llewelyn at gwynethllewelyn dot net ¶

4 months ago

If you're trying to merge an array with something that evaluates to NULL, you'll get unpredictable results:

<?php
        $a = ['1', '2', '4'];
        $b = null;

        var_dump($a);
        var_dump($b);

        $c = array_merge($a, $b);  // this won't work
        echo "The merged array is:";
        var_dump($c);
?>

Depending on your error setting, you might not even get anything at all.

Under PHP 7.4:

array(3) {
  [0]=>
  string(1) "1"
  [1]=>
  string(1) "2"
  [2]=>
  string(1) "4"
}
NULL
PHP Warning:  array_merge(): Expected parameter 2 to be an array, null given in /home/gwyneth/stupid-test.php on line 8
The merged array is: NULL

Under PHP 8.{0,1,2}:

array(3) {
  [0]=>
  string(1) "1"
  [1]=>
  string(1) "2"
  [2]=>
  string(1) "4"
}
NULL
PHP Fatal error:  Uncaught TypeError: array_merge(): Argument #2 must be of type array, null given in /home/gwyneth/stupid-test.php:8
Stack trace:
#0 /home/gwyneth/stupid-test.php(8): array_merge()
#1 {main}
  thrown in /home/gwyneth/stupid-test.php on line 8

Depending on your display/debug settings, you might not even get anything.

The solution, of course, is to do a quick & dirty test before passing the 2nd argument:

<?php
        $a = ['1', '2', '4'];
        $b = null;

        var_dump($a);
        var_dump($b);

        $c = array_merge($a, $b ?? []);
        echo "The merged array is:";
        var_dump($c);
?>

Which gives the expected result (PHP 7.4 to PHP 8.2):

array(3) {
  [0]=>
  string(1) "1"
  [1]=>
  string(1) "2"
  [2]=>
  string(1) "4"
}
NULL
The merged array is:array(3) {
  [0]=>
  string(1) "1"
  [1]=>
  string(1) "2"
  [2]=>
  string(1) "4"
}

While it's perfectly legitimate to merge empty arrays, null is *not* an empty array!

down

-6

php at k dot ull dot at ¶

1 year ago

Merge two arrays and retain only unique values.
Append values from second array.
Do not care about keys.

$array1 = [
    0 => 'apple',
    1 => 'orange',
    2 => 'pear',
];

$array2 = [
    0 => 'melon',
    1 => 'orange',
    2 => 'banana',
];

$result = array_keys(
    array_flip($array1) + array_flip($array2)
);

Result:
[
  [0] => "apple",
  [1] => "orange",
  [2] => "pear",
  [3] => "melon",
  [4] => "banana",
}

＋add a note