array_merge

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

array_merge — Combina um ou mais arrays

Descrição

array_merge(array ...$arrays): array

Combina os elementos de dois ou mais arrays de forma que os elementos de um são colocados no final do array anterior. Retorna o array resultante da fusão.

Se os arrays dados têm as mesmas chaves string, então o último valor para uma chave irá sobrescrever o valor anterior. Se, no entanto, os arrays tem as mesmas chaves numéricas, o último valor para uma chave não sobrescreverá o valor original, e sim adicionado ao array resultante.

Se apenas um array é dado e o array é indexado numericamente, as chaves são reindexadas de uma maneira contínua.

Parâmetros

arrays: Uma lista de arrays a combinar.

Valor Retornado

Retorna o array resultante. Se chamado sem argumentos, retorna um array vazio.

Changelog

Versão	Descrição
7.4.0	A função agora pode ser chamada sem argumentos. Anteriormente, ao menos um parâmetro era necessário.

Exemplos

Exemplo #1 Exemplo de array_merge()

<?php
$array1 = array("cor" => "vermelho", 2, 4);
$array2 = array("a", "b", "cor" => "verde", "forma" => "trapezoide", 4);
$result = array_merge($array1, $array2);
print_r($result);
?>

O exemplo acima produzirá:

Array
(
    [cor] => verde
    [0] => 2
    [1] => 4
    [2] => a
    [3] => b
    [forma] => trapezoide
    [4] => 4
)

Exemplo #2 Exemplo simples de array_merge()

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

Não esqueça que as chaves numéricas serão reordenadas!

Array
(
    [0] => data
)

Se você deseja apenas adicionar os elementos do segundo array no primeiro, sem sobrescrever os elementos e sem causar a reindexação, utilize o operador +:

<?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);
?>

As chaves do primeiro array são preservadas. Se uma chave existir em dois arrays, então o elemento do primeiro array será preservado e o elemento de mesma chave no segundo array será descartado.

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"
}

Exemplo #3 array_merge() com tipos não array

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

O exemplo acima produzirá:

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

Veja Também

array_merge_recursive() - Mescla um ou mais arrays recursivamente
array_replace() - Substitui elementos de arrays passados no primeiro array
array_combine() - Cria um array usando um array para chaves e outro para valores
array operators

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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",
}

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