Merge keys of an array based on values - php

Question

I want to merge the keys of array based on values. This is my array.
Array
(
[1] => 1
[2] => 1
[3] => 1
[4] => 2
[5] => 0
[6] => 2
[7] => 2
)
I want output as
Array
(
[1,2,3] => 1
[4,6,7] => 2
[5] => 0
)
I have been brain storming entire day but couldn't find a solution. Any hint would be much appreciated.
WHAT I HAVE TRIED:
for($i=2;$i<=count($new);$i++){
if ($new[$i-1][1]==$new[$i][1]){
$same .= $new[$i-1][0].$new[$i][0];
}
}
echo $same;
But I am stucked. I am comparing the keys one by one but it's very complicated. I don't need the code. I only need the hint or logic. Anyone kind enough?

Answer 1

<?php
$old_arr = ["1"=>1,"2"=>1,"3"=>1,"4"=>2,"5"=>0,"6"=>2,"7"=>2];
$tmp = array();
foreach($old_arr as $key=>$value)
{
if(in_array($value, $tmp)){
$index = array_search($value, $tmp);
unset($tmp[$index]);
$tmp[$index.",".$key] = $value;
}else{
$tmp[$key] = $value;
}
}
ksort($tmp);
echo "<pre>";
print_r($tmp);
echo "</pre>";
?>
https://eval.in/529314

Answer 2

You can loop through array elements and create a new array with new structure. Please check the below code it may help you
$old_array = array(1=> 1,2 => 1,
3=> 1,
4 => 2,
5 => 0,
6 => 2,
7 => 2
);
$new_array = array();
foreach($old_array as $key => $value)
{
if(in_array($value,$new_array))
{
$key_new = array_search($value, $new_array);//to get the key of element
unset($new_array[$key_new]); //remove the element
$key_new = $key_new.','.$key; //updating the key
$new_array[$key_new] = $value; //inserting new element to the key
}
else
{
$new_array[$key] = $value;
}
}
print_r($new_array);

Answer 3

$arr = array(1 => 1, 2 => 1, 3 => 1, 4 => 2, 5 => 0, 6 => 2, 7 => 2);
$tmp = array();
foreach ($arr as $key => $val)
$tmp[$val][] = $key;
$new = array();
foreach ($tmp as $key => $val)
$new[implode(',', $val)] = $key;
First loop the original array through, creating a temporary array, where your original values are keys and values are the original keys as an array.
Then loop the temporary array, creating the new array, where the temporary array's values are imploded as keys.

Answer 4

There's no way to have an array of keys to a single value, but the other way around:
function flipWithKeyArray($arr){
$result = array();
foreach($arr as $key => $val){
if(!isset($result[$val]))
$result[$val] = array();
$result[$val][] = $key;
}
return $result;
}
This will flip your array and declare one array per value of your old array and then push the keys with the same value into each list.
For an array like this:
array(1=>1, 2=>1, 3=>1, 4=>2, 5=>2, 6=>2)
The result will look like this:
array(1=>array(1,2,3), 2=>array(4,5,6))
Hope it fits your need.