How can I combine array's items?

Question

Here is my code:

$arr = [
    0 => [1, 2, 3, 4],
    1 => ['one', 'two', 'three', 'four'] 
    ];

$res = [];    
foreach ($arr as $item){
    foreach($item as $i){
        $res = [$i, $item];
    }
}

print_r($res);

/*
Array
(
    [0] => four
    [1] => Array
        (
            [0] => one
            [1] => two
            [2] => three
            [3] => four
        )

)

As you see the result doesn't make any sense. Here is expected result:

Array
(
    [0] => Array
        (
            [0] => 1
            [1] => one
        )
    [1] => Array
        (
            [0] => 2
            [1] => two
        )
    [2] => Array
        (
            [0] => 3
            [1] => three
        )
    [3] => Array
        (
            [0] => 4
            [1] => four
        )
)

You know, nested loops always make me confuse. Anyway, does anybody know how can I achieve to the expected result?

Answer 1

Update:

Or, as noted below by Shafizadeh, simply:

<?php
$arr = [
    [1, 2, 3, 4],
    ['one', 'two', 'three', 'four']
];

$out = array_map(null, ...$arr);

---

This?

<?php
$arr = [
    [1, 2, 3, 4],
    ['one', 'two', 'three', 'four']
];

// array_map accepts an open number of input arrays and applies
// a given callback on each *set* of *i-th* values from these arrays.
// The return value of the callback will be the new array value
// of the final array:
                            // get all function arguments as an array
$out = array_map(function (...$r) {
    return $r;
}, ...$arr); // *spread* input array as individual input arguments

print_r($out);

// Array
// (
//     [0] => Array
//         (
//             [0] => 1
//             [1] => one
//         )
// 
//     [1] => Array
//         (
//             [0] => 2
//             [1] => two
//         )
// ...

Demo: https://3v4l.org/uJNKG

Ref: http://php.net/manual/functions.arguments.php#functions.variable-arg-list.new

Answer 2

Try to imagine what you would do if you would do this by hand:

• First step: Take a value from array A and a value from array B at a cretain position (Let's call it $i).
• Second step: Add those two values to a new array C.
• Third step: Increase $i by one
• Fourth Step: repeat this until you have looped through the whole array.

Answer 3

You can use array_column() for that purpose with a single for loop.

$arr = [
    0 => [1, 2, 3, 4],
    1 => ['one', 'two', 'three', 'four'] 
    ];

$res = [];    
foreach ($arr[0] as $key => $val){
     $res[] = array_column($arr, $key);
}

Here's working example: https://3v4l.org/vXdvD

Answer 4

Iterate over the first sub-array using the $key => $value syntax of foreach, combining the element at the iteration index (i.e. $item) with the corresponding element from the second sub-array (i.e. $arr[1][$key]):

foreach ($arr[0] as $key => $item) {
    $res[] = [$item, $arr[1][$key] ];
}

See an demonstration here

Update

I admit I learned from Yoshi's answer about the spread operator - I knew it existed in JavaScript but not PHP. The explanation below starts applying array_map() without the spread operator and then applies it.

To start applying array_map() the first parameter is the anonymous function, which returns the two arguments it accepts in a single array. The second and third parameters are the two sub-arrays.

$arr = [
    0 => [1, 2, 3, 4],
    1 => ['one', 'two', 'three', 'four'] 
    ];

$res = array_map(function($item0, $item1) {
    return [ $item0, $item1];
}, $arr[0], $arr[1]);

print_r($res);

See the demonstration here.

Then taking that code, the spread operator can be used to substitute for the arguments of the anonymous function (i.e. $item0, $item1) as well as the second and third arguments to array_map() (i.e. $arr[0], $arr[1])

$res = array_map(function(...$items) {
    return $items;
}, ...$arr);

See the demonstration for that here.

Answer 5

$arr = [
  0 => [1, 2, 3, 4],
  1 => ['one', 'two', 'three', 'four']
];
$res = [];
foreach ($arr[0] as $key => $item) {
  $res[] = [$item, $arr[1][$key] ];
}
print_r($res);