How to interpolate two arrays? [duplicate] - php

Question

This question already has answers here:
Merge two flat indexed arrays of equal size so that values are pushed into the result in an alternating fashion
(2 answers)
Closed 6 months ago.
I have two arrays:
A = [1, 2, 3, 4]
B = ['a', 'b', 'c', 'd']
I want to merge them into tuples (A, B) in an one-dimensional array:
C = [1, 'a', 2, 'b', 3, 'c', 4, 'd']
Is there some native function in PHP that lets you interpolate two arrays this way? If not, would a loop be the most effective and eficient way to do this?
The number of elements of A will always be the same of B.
Note: If it helps, in the context of my specific needs, array A can be summarized as a single value (since the value will be the same for all values in B).
A = 1
B = ['a', 'b', 'c', 'd']
C = [1, 'a', 1, 'b', 1, 'c', 1, 'd']

Answer 1

Loops are OK in this case, since PHP does not have a native function to interleave 2 arrays, but this is a nice way to solve the problem:
function interleave($array1, $array2) {
$result = array();
array_map(function ($e1, $e2) use (&$result) {
array_push($result, $e1, $e2);
}, $array1, $array2);
return $result;
}

Answer 2

I don't know if there is any built-in mapping function that makes this easier, but this is a simple, naive implementation.
$a = array(1,2,3,4);
$b = array('a','b','c','d');
function array_interpolate($a, $b) {
if (sizeof($a) != sizeof($b))
throw new Exception('Arrays must be of same size');
$result = array();
for ($i = 0, $l = sizeof($a); $i < $l; $i++) {
$result[2*$i] = $a[$i];
$result[2*$i+1] = $b[$i];
}
return $result;
}
$res = array_interpolate($a, $b);
print_r($res);
The above returns
Array
(
[0] => 1
[1] => a
[2] => 2
[3] => b
[4] => 3
[5] => c
[6] => 4
[7] => d
)

Answer 3

$C = call_user_func_array('array_merge', call_user_func_array('array_map', array(NULL, $A, $B)));

Answer 4

Since in PHP arrays are implemented as hash tables (Hash table on wikipedia), you won't be able to achieve your goal faster then looping through array.
Here is a simplest example:
function interpolate(array $a,array $b) {
$result = array();
for($i = 0; $i < count($a); $i++) {
$result[] = $a[$i];
$result[] = $b[$i];
}
return $result;
}