Without built-in functions how to find differences in two arrays - php

Question

I have to find the difference for both array, i have tried but i am not getting my expected.can you please help here.
<?php
$firstArray = array(3,4,5,6);
$secondArray = array(4, 5);
$outputArray = array();
foreach($firstArray as $firstArrayItem) {
foreach($secondArray as $secondArrayItem) {
if($firstArrayItem != $secondArrayItem) {
$outputArray[] = $firstArrayItem;
}
}
}
print_r($outputArray);
Expected output
[3,6]
Note: we should not use PHP inbuild functions.

Answer 1

a) Use a boolean value to check it:
<?php
$firstArray = array(3,4,5,6);
$secondArray = array(4, 5);
$outputArray = array();
foreach($firstArray as $firstArrayItem) {
$found = false;
foreach($secondArray as $secondArrayItem) {
if($firstArrayItem == $secondArrayItem) {
$found = true;
}
}
if($found == false){
$outputArray[] = $firstArrayItem;
}
}
print_r($outputArray);
Output: https://3v4l.org/8CuS8
b) Another way using for() loop: https://3v4l.org/9JZrW

Answer 2

Here is a solution that does not give a different result when the input arrays as swapped.
So it will give the same result for this:
$firstArray = array(3, 4, 5, 6);
$secondArray = array(4, 5);
as for this:
$firstArray = array(4, 5);
$secondArray = array(3, 4, 5, 6);
Also, it will deal with duplicate values as follows:
$firstArray = array(4, 4, 4);
$secondArray = array(3, 4, 6);
for which I would expect the output to be:
array(3, 4, 4, 6) // Only one 4 is common and should be excluded.
The code for having this behaviour could be (without inbuilt functions except for print_r):
$assoc = [];
foreach($firstArray as $value) {
$assoc[$value][] = 1;
}
foreach($secondArray as $value) {
$assoc[$value][] = -1;
}
foreach($assoc as $value => $list) {
$count = 0;
foreach($list as $delta) $count += $delta;
for($i = $count > 0 ? $count : -$count; $i > 0; $i--) {
$result[] = $value;
}
}
print_r($result);

Answer 3

$firstArray = array(3,4,5,6);
$secondArray = array(4, 5, 7);
$outputArray = diffArray($firstArray, $secondArray);
$outputArray = diffArray($secondArray, $firstArray, $outputArray);
function diffArray($arr1, $arr2, $result = array()) {
foreach($arr1 as $arr11) {
$isExist = false;
foreach($arr2 as $arr22) {
if($arr11 === $arr22) {
$isExist = true;
}
}
if(!$isExist) $result[] = $arr11;
}
return $result;
}
print_r($outputArray);