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array_merge

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

array_mergeCombina dos o más arrays

Descripción

array_merge(array $array1, array $... = ?): array

Combina los elementos de uno o más arrays juntándolos de modo que los valores de uno se anexan al final del anterior. Retorna el array resultante.

Si los arrays de entrada tienen las mismas claves de tipo string, el último valor para esa clave sobrescribirá al anterior. Sin embargo, los arrays que contengan claves numéricas, el último valor no sobrescribirá el valor original, sino que será añadido al final.

Los valores del array de entrada con claves numéricas serán renumeradas con claves incrementales en el array resultante, comenzando desde cero.

Parámetros

array1

Array inicial a combinar.

...

Lista variable de arrays para combinar.

Valores devueltos

Retorna el array resultante.

Ejemplos

Ejemplo #1 Ejemplo de array_merge()

<?php
$array1    
= array("color" => "red"24);
$array2    = array("a""b""color" => "green""shape" => "trapezoid"4);
$resultado array_merge($array1$array2);
print_r($resultado);
?>

El resultado del ejemplo sería:

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

Ejemplo #2 Ejemplo de sencillo de array_merge()

<?php
$array1    
= array();
$array2    = array(=> "data");
$resultado array_merge($array1$array2);
?>

¡No olvidarse de que las claves numéricas serán renumeradas!

Array
(
    [0] => data
)

Para anexar elementos del segundo array al primer array entretanto no se sobrescriban los elementos del primer array y no se reindexe, se ha de utilizar el operador + de unión de arrays.

<?php
$array1    
= array(=> 'zero_a'=> 'two_a'=> 'three_a');
$array2    = array(=> 'one_b'=> 'three_b'=> 'four_b');
$resultado $array1 $array2;
var_dump($resultado);
?>

Las claves del primer array se preservaran. Si una clave existe en ambos arrays, se usará el elemento del primer array, y el elemento de la clave coincidente del segundo array será ignorado.

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"
}

Ejemplo #3 array_merge() con tipos que no son array

<?php
$comienzo 
'foo';
$fin = array(=> 'bar');
$resultado array_merge((array)$comienzo, (array)$fin);
print_r($resultado);
?>

El resultado del ejemplo sería:

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

Ver también

add a note

User Contributed Notes 5 notes

up
291
Julian Egelstaff
13 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
up
20
ChrisM
9 months 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
up
4
Andreas Hofmann
10 months 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.
up
2
JoshE
6 months 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
up
9
fsb at thefsb dot org
2 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
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