Php merge array key and value

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Источник

array_merge

Merges the elements of one or more arrays together so that the values of one are appended to the end of the previous one. It returns the resulting 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

Variable list of arrays to merge.

Return Values

Returns the resulting array. If called without any arguments, returns an empty array .

Changelog

Version	Description
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

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

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:

$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 );
?>

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

$beginning = ‘foo’ ;
$end = array( 1 => ‘bar’ );
$result = array_merge ((array) $beginning , (array) $end );
print_r ( $result );
?>

The above example will output:

User Contributed Notes 8 notes

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.

$array1 [ 0 ] = «zero» ;
$array1 [ 1 ] = «one» ;

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

$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.

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:

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

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

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

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:

$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:

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

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

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

You will get both:

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

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

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

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

$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.

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

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
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:

$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):

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

Источник

PHP array_merge() Function

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

Parameter Values

Parameter	Description
array1	Required. Specifies an array
array2	Optional. Specifies an array
array3.	Optional. Specifies an array

Technical Details

Return Value:	Returns the merged array
PHP Version:	4+
Changelog:	As of PHP 5.0, this function only accept parameters of type array

More Examples

Example

Merge two associative arrays into one array:

Example

Using only one array parameter with integer keys:

Источник

Php merge array key and value