❮ PHP Array Reference
Example
Merge two arrays into one array:
Try it Yourself »
Definition and Usage
The array_merge[] function merges one or more arrays into one array.
Tip: You can assign one array to the function, or as many as you like.
Note: If two or more array elements have the same key, the last one overrides the others.
Note: If you assign only one array to the array_merge[] function, and the keys are integers, the function returns a new array with integer keys starting at 0 and increases by 1 for each value [See example below].
Tip: The difference between this function and the array_merge_recursive[] function is when two or more array elements have the same key. Instead of override the keys, the array_merge_recursive[] function makes the value as an array.
Syntax
array_merge[array1, array2, array3, ...]
Parameter Values
| array1 | Required. Specifies an array |
| array2 | Optional. Specifies an array |
| array3,... | Optional. Specifies an array |
Technical Details
| Returns the merged array |
| 4+ |
| As of PHP 5.0, this function only accept parameters of type array |
More Examples
Example
Merge two associative arrays into one array:
Try it Yourself »
Example
Using only one array parameter with integer keys:
Try it Yourself »
❮ PHP Array Reference
[PHP 4, PHP 5, PHP 7, PHP 8]
array_merge — Merge one or more arrays
Description
array_merge[array ...$arrays]: array
If the input arrays have the same string keys, then the later value for that key will overwrite the previous one. If, however, the arrays contain numeric keys, the later value will not overwrite the original value, but will be appended.
Values in the input arrays with numeric keys will be renumbered with incrementing keys starting from zero in the result array.
Parameters
arraysVariable list of arrays to merge.
Return Values
Returns the resulting array. If called without any arguments, returns an empty array.
Changelog
| 7.4.0 | This function can now be called without any parameter. Formerly, at least one parameter has been required. |
Examples
Example #1 array_merge[] example
The above example will output:
Array
[
[color] => green
[0] => 2
[1] => 4
[2] => a
[3] => b
[shape] => trapezoid
[4] => 4
]
Example #2 Simple array_merge[] example
Don't forget that numeric keys will be renumbered!
If you want to append array elements from the second array to the first array while not overwriting the elements from the first array and not re-indexing, use the + array union operator:
The keys from the first array will be preserved. If an array key exists in both arrays, then the element from the first array will be used and the matching key's element from the second array will be ignored.
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"
}
Example #3 array_merge[] with non-array types
The above example will output:
Array
[
[0] => foo
[1] => bar
]
See Also
- array_merge_recursive[] - Merge one or more arrays recursively
- array_replace[] - Replaces elements from passed arrays into the first array
- array_combine[] - Creates an array by using one array for keys and another for its values
- array operators
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:
--Julian
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.
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 8.0:
PHP 7.4:
1.2135608196259 sec for spread
1.1402177810669 sec for array_merge
1.1952061653137 sec for spread
1.099925994873 sec for array_merge
Andreas Hofmann ¶
9 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:
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:
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.
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