array_merge

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

array_merge — Fusiona varios arrays en uno solo

Descripción

array_merge(array ...$arrays): array

array_merge() reúne los elementos de uno o varios arrays añadiendo los valores de uno al final del otro. El resultado es un array.

Si los arrays de entrada tienen claves en común, entonces, el valor final para esa clave sobrescribirá el anterior. Sin embargo, si los arrays contienen claves numéricas, el valor final no sobrescribirá el valor original, sino que será añadido.

Las claves numéricas de los arrays de entrada serán renumeradas en claves incrementadas partiendo de cero en el array fusionado.

Parámetros

arrays: Lista de arrays variables a fusionar.

Valores devueltos

Devuelve el array resultante. Si es llamado sin argumentos, devuelve un array vacío.

Historial de cambios

Versión	Descripción
7.4.0	Esta función puede ahora ser llamada sin parámetros. Anteriormente, al menos un parámetro era requerido.

Ejemplos

Ejemplo #1 Ejemplo con 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);
?>

El resultado del ejemplo sería:

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

Ejemplo #2 Ejemplo simple con array_merge()

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

¡No olvide que los índices numéricos serán reindexados!

Array
(
    [0] => data
)

Si se desea añadir elementos del segundo array al primero sin sobrescribir o reindexar los elementos del primero, utilice el operador de unión + :

<?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);
?>

Las claves del primer array son preservadas. Si una clave existe en los 2 arrays, entonces el elemento del primero será utilizado y la clave correspondiente del segundo será ignorada.

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 Ejemplo con array_merge() con tipos no-array

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

El resultado del ejemplo sería:

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

Ver también

array_merge_recursive() - Combina uno o varios arrays juntos, de manera recursiva
array_replace() - Sustituye los elementos de un array por los de otros arrays
array_combine() - Crea un array a partir de otros dos arrays
los operadores de array

Found A Problem?

Learn How To Improve This Page • Submit a Pull Request • Report a Bug

＋add a note

User Contributed Notes 4 notes

down

311

Julian Egelstaff ¶

15 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 ¶

3 years 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 ¶

3 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 ¶

5 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

＋add a note