Combine two arrays into a string - php

Question

I need to create a new array called ar1 with the items: [Dublin, Budapest, Copenhagen] and ar2 with [Ireland, Hungary, Denmark] after than answer with a string containing each country from the countries-array followed by the corresponding capital. Use the format "country = capital,
* country = capital..."
Check code below but i know that is another way to doing that ex. For loop but can someone explain me how?
$ar1 = ["Dublin", "Budapest", "Copenhagen"];
$ar2 = ["Ireland", "Hungary", "Denmark"];
$ANSWER = $ar2[0] . " = " . $ar1[0] . ", " . $ar2[1] . " = " . $ar1[1]. ", " . $ar2[2] . " = " . $ar1[2];

Answer 1

You should use a foreach and the key.
$ar1 = ["Dublin", "Budapest", "Copenhagen"];
$ar2 = ["Ireland", "Hungary", "Denmark"];
$ANSWER = '';
foreach($ar1 as $key => $capital) {
$ANSWER .= $ar2[$key] . ' = ' . $capital . ', ';
}
echo rtrim($ANSWER, ', ');
... and then rtrim to remove the last ,.
https://3v4l.org/f8PJN

Answer 2

Another way to do it using array_combine()
<?php
$ar1 = ["Dublin", "Budapest", "Copenhagen"];
$ar2 = ["Ireland", "Hungary", "Denmark"];
$result = array_combine($ar2,$ar1);
$ANSWER = '';
$i = 0;
$comma = ', ';
$len = count($result);
foreach($result as $country => $capital) {
if ($i == $len - 1){
$comma='';
}
$ANSWER .= $country . ' = ' . $capital.$comma;
$i++;
}
echo $ANSWER;
DEMO: https://3v4l.org/WGtJ3
Using array_map()
$ar1 = ["Dublin", "Budapest", "Copenhagen"];
$ar2 = ["Ireland", "Hungary", "Denmark"];
$input = array_combine($ar2,$ar1);
$output = implode(', ', array_map(
function ($v, $k) { return sprintf("%s=%s", $k, $v); },
$input,
array_keys($input)
));
echo $output;
DEMO: https://3v4l.org/qps1G

Answer 3

More fast and simple way:
$countries=["Ireland", "Hungary", "Denmark"];
$capitals=["Dublin", "Budapest", "Copenhagen"];
$string=implode(',',array_map(function($country,$capital){ return "$country=$capital";},$countries,$capitals));
var_dump($string);
output:
string(50) "Ireland=Dublin,Hungary=Budapest,Denmark=Copenhagen"

Answer 4

If you've got two related lists in separate variables, it's often easier to transpose them into a single structure first. In PHP, you can do this like so:
$transposed = array_map(null, $ar1, $ar2);
Once they're combined, it's a lot more simple to generate the required output:
echo implode(', ', array_map(function($row) {
return "{$row[1]} = {$row[0]}";
}, $transposed));
Ireland = Dublin, Hungary = Budapest, Denmark = Copenhagen
See https://3v4l.org/LfvIY