There are 3 operations with sets in mathematics: intersection, difference and union (unification). In PHP we can do this operations with arrays:
- intersection:
array_intersect - difference:
array_diff
What function is for union?
No duplicates can be in the result array (like array_intersect and array_diff).
If indexes are numeric then array_merge will not overwrite the original value, but will be appended (PHP docs).
Answer：
array_unique( array_merge( ... ) )
Answer：
Adrien’s answer won’t necessary produce a sequentially numbered array from two sequentially numbered arrays – here are some options that will:
array_values(array_unique(array_merge($array1, $array2)));
(Adrien’s answer with renumbering the keys afterward)
array_keys(array_flip($array1)+array_flip($array2))
(Put the values in the keys, and use the array union operator)
array_merge($array1, array_diff($array2, $array1))
(Remove the shared values from the second array before merging)
Benchmark results (for merging two arrays of length 1000 a thousand times on my system):
- Unique (Adrien’s version): 2.862163066864 seconds
- Values_Unique: 3.12 seconds
- Keys_Flip: 2.34 seconds
- Merge_Diff: 2.64 seconds
Same test, but with the two arrays being very similar (at least 80% duplicate):
- Unique (Adrien’s version): 2.92 seconds
- Values_Unique: 3.15 seconds
- Keys_Flip: 1.84 seconds
- Merge_Diff: 2.36 seconds
It seems using the array union operator to do the actual union is the fastest method. Note however that array_flip is only safe if the array’s values are all strings or all integers; if you have to produce the union of an array of objects, I recommend the version with array_merge and array_diff.
Answer：
Use array_unique and array_merge together.
Answer：
use “+” operator to do so. See the link Array Operators
Answer：
From the code in the PHP: Array Operators documentation:
<?php
$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");
$c = $a + $b; // Union of $a and $b
echo "Union of $a and $b: \n";
var_dump($c);
$c = $b + $a; // Union of $b and $a
echo "Union of $b and $a: \n";
var_dump($c);
?>
When executed, this script will print the following:
Union of $a and $b:
array(3) {
["a"]=>
string(5) "apple"
["b"]=>
string(6) "banana"
["c"]=>
string(6) "cherry"
}
Union of $b and $a:
array(3) {
["a"]=>
string(4) "pear"
["b"]=>
string(10) "strawberry"
["c"]=>
string(6) "cherry"
}
Answer：
$result = array_merge_recursive($first, $second);
can be useful when you have arrays with arrays inside.
Answer：
The + operator:
$x[0] = 4;
$x[1] = 1;
$y[0] = 9;
$y[2] = 5;
$u = $y + $x;
// Results in:
$u[0] === 9;
$u[1] === 1;
$u[2] === 5;
Note that $x + $y != $y + $x
Answer：
The OP did not specify whether the union is by value or by key and PHP has array_merge for merging values and + for merging the keys. The results depends on whether the array is indexed or keyed and which array comes first.
$a = ['a', 'b'];
$b = ['b', 'c'];
$c = ['a' => 'A', 'b' => 'B'];
$d = ['a' => 'AA', 'c' => 'C'];
Indexed array
See array_merge
By value using array_merge
array_merge($a, $b); // [0 => 'a', 1 => 'b', 2 => 'b', 3 => 'c']
array_merge($b, $a); // [0 => 'b', 1 => 'c', 2 => 'a', 3 => 'b']
merge by key using + operator
See + operator
$a + $b; // [0 => 'a', 1 => 'b']
$b + $a; // [0 => 'b', 1 => 'c']
Keyed array
By value using array_merge
array_merge($c, $d); // ['a' => 'AA', 'b' => 'B', 'c' => 'C']
array_merge($d, $c); // ['a' => 'A', 'c' => 'C', 'b' => 'B']
merge by key using + operator
$c + $d; // ['a' => 'A', 'b' => 'B', 'c' => 'C']
$d + $c; // ['a' => 'AA', 'c' => 'C', 'b' => 'B']
Answer：
Just use $array1 + $array2
It will result union of both array.
