How to group of 2 arrays - php

Question

I have 2 arrays like this
$head = array(7, 1, 1, 1, 1, 14, 14, 14, 9, 9, 9, 13, 13, 13, 3, 3, 5, 8, 8, 8, 2, 2); //count =22
$customer = array(1, 7, 9, 13, 14, 1, 9, 13, 1, 13, 14, 1, 9, 14, 2, 8, 8, 2, 3, 5, 3, 8); //count=22
And I want to group this 2 arrays by consider at $customer, if $customer[0]=1 in $customer[1-21] and $head[1-21] will not have a value 1, such as in the $head[1] have a value 1, So delete at $head[1] and $customer[1]. And then consider at $customer[6]. The value is 9. It means in $head[7-21] and $customer[7-21] will not have a value 9.
I am trying to write a code for this concept like this. Here is my code
for ($i = 0; $i < count($head); $i++) {
for ($j = $i + 1; $j < count($customer); $j++) {
if ($customer[$i] == $head[$j]) {
unset($head[$j]);
unset($customer[$j]);
}
if ($customer[$i] == $customer[$j]) {
unset($head[$j]);
unset($customer[$j]);
}
}
}
print_r($head);
print_r($customer);
the result is of $head and $customer is:
Array ( [0] => 7 [6] => 14 [7] => 14 [13] => 13 [14] => 3 [15] => 3 [16] => 5 [17] => 8 [18] => 8 [19] => 8 [20] => 2 [21] => 2 )
Array ( [0] => 1 [6] => 9 [7] => 13 [13] => 14 [14] => 2 [15] => 8 [16] => 8 [17] => 2 [18] => 3 [19] => 5 [20] => 3 [21] => 8 )
I found that it's wrong. Because the real result should be:
Array ( [0] => 7 [6] => 14 [7] => 14 [14] => 3 [15] => 3 )
Array ( [0] => 1 [6] => 9 [7] => 13 [14] => 2 [15] => 8 )
Please help me to fix this problem.

Answer 1

Your logic is all ok but when you unset a particular index then all other index after when you iterate it again then i index is missing. Just open the error and warning then you will see
Notice: Undefined offset
I have just replaced your uset to assign it to ''. So you can understand it
<?php
$head = array(7, 1, 1, 1, 1, 14, 14, 14, 9, 9, 9, 13, 13, 13, 3, 3, 5, 8, 8, 8, 2, 2); //count =22
$customer = array(1, 7, 9, 13, 14, 1, 9, 13, 1, 13, 14, 1, 9, 14, 2, 8, 8, 2, 3, 5, 3, 8); //count=22
for ($i = 0; $i < count($head); $i++) {
for ($j = $i + 1; $j < count($customer); $j++) {
if ($customer[$i] == $head[$j]) {
$head[$j] = '';
$customer[$j] = '';
}
if ($customer[$i] == $customer[$j]) {
$head[$j] = '';
$customer[$j] = '';
}
}
}
print_r(array_diff($head, [''])); // remove all the '' entries
print_r(array_diff($customer, [''])); // remove all the '' entries

Answer 2

The problem is that count() only returns a count of the set elements in the array. So if you unset them it will be reduced and you won't arrive at the end of the array. To fix, calculate the count at the start and store in a variable:
$headcount = count($head);
$customercount = count($customer);
for ($i = 0; $i < $headcount; $i++) {
for ($j = $i + 1; $j < $customercount; $j++) {
if ($customer[$i] == $head[$j]) {
unset($head[$j]);
unset($customer[$j]);
}
if ($customer[$i] == $customer[$j]) {
unset($head[$j]);
unset($customer[$j]);
}
}
}