Remove duplicates from a multidimensional array based on multiple keys - php

Question

Sorry if this was asked before, but I searched a lot and couldn't find a solution.
I've been trying to solve this problem for a while now, and couldn't write the function for it.
I have an array like that:
$numbers = array(
array("tag" => "developer", "group" => "grp_1", "num" => "123123"),
array("tag" => "developer", "group" => "grp_2", "num" => "111111"),
array("tag" => "student", "group" => "grp_1", "num" => "123123"),
array("tag" => "student", "group" => "grp_2", "num" => "123123"),
array("tag" => "developer", "group" => "grp_3", "num" => "111111"),
);
I need to write a function, that removes the duplicates off this array, based on multiple keys, so my function call should look something like that:
unique_by_keys($numbers, array("num","group"));
In other terms, one number can't be in the same group more than once.
After calling unique_by_keys() by array should be like that:
$numbers = array(
array("tag" => "developer", "group" => "grp_1", "num" => "123123"),
array("tag" => "developer", "group" => "grp_2", "num" => "111111"),
array("tag" => "student", "group" => "grp_2", "num" => "123123"),
array("tag" => "developer", "group" => "grp_3", "num" => "111111"),
);
I'd appreciate if you could help me find a solution, or lead me to the correct way of thinking.
Thanks!
SOLUTION:
I was able to find a solution, by writing the following function:
( I wrote it in a way that accepts many forms of $haystack arrays )
function unique_by_keys($haystack = array(), $needles = array()) {
if (!empty($haystack) && !empty($needles)) {
$_result = array();
$result = array();
$i = 0;
foreach ($haystack as $arrayObj) {
if (is_array($arrayObj)) {
$searchArray = array();
foreach ($needles as $needle) {
if (isset($arrayObj[$needle])) {
$searchArray[$needle] = $arrayObj[$needle];
}
}
if (!in_array($searchArray, $_result)) {
foreach ($arrayObj as $key => $value) {
if (in_array($key, $needles)) {
$_result[$i][$key] = $value;
}
}
$result[] = array_merge($_result[$i], $arrayObj);
}
} else {
$result[] = $arrayObj;
}
$i++;
}
return $result;
}
}
Thanks for everyone that replied!

Answer 1

Bhaskar's approach which assigns unique keys in the loop to remove duplicates affords a very small function for this case.
Here is a previous and unnecessarily complicated version:
function unique_by_keys($haystack=array(),$needles=array()){
// reverse order of sub-arrays to preserve lower-indexed values
foreach(array_reverse($haystack) as $row){
$result[implode('',array_intersect_key($row,array_flip($needles)))]=$row; // assign unique keys
}
ksort($result); // sort the sub-arrays by their assoc. keys
return array_values($result); // replace assoc keys with indexed keys
}
This is the best/leanest solution I can come up with:
$numbers = array(
array("tag" => "developer", "group" => "grp_1", "num" => "123123"),
array("tag" => "developer", "group" => "grp_2", "num" => "111111"),
array("tag" => "student", "group" => "grp_1", "num" => "123123"),
array("tag" => "student", "group" => "grp_2", "num" => "123123"),
array("tag" => "developer", "group" => "grp_3", "num" => "111111")
);
function unique_by_keys($haystack=array(),$needles=array()){
foreach($haystack as $row){
$key=implode('',array_intersect_key($row,array_flip($needles))); // declare unique key
if(!isset($result[$key])){$result[$key]=$row;} // save row if non-duplicate
}
return array_values($result);
}
echo "<pre>";
var_export(unique_by_keys($numbers,array("group","num")));
echo "</pre>";
Output:
array (
0 =>
array (
'tag' => 'developer',
'group' => 'grp_1',
'num' => '123123',
),
1 =>
array (
'tag' => 'developer',
'group' => 'grp_2',
'num' => '111111',
),
2 =>
array (
'tag' => 'student',
'group' => 'grp_2',
'num' => '123123',
),
3 =>
array (
'tag' => 'developer',
'group' => 'grp_3',
'num' => '111111',
),
)

Answer 2

$newNumbers = array();
foreach($numbers as $key=>$values){
$newkey = $values['group'].'__'.$values['num'];
$newNumbers[$newkey] = $values;
}
var_dump($newNumbers)

Answer 3

Code might not be efficient, but i will work for you :)
$result = unique_by_keys($numbers, array("num","group"));
echo "<pre>";
print_R($result);
function unique_by_keys($numbers, $arr){
$new_array = array();
$output = array();
foreach ($numbers as $n){
if(isset($new_array[$n[$arr[1]]]) && $new_array[$n[$arr[1]]] == $n[$arr[0]]){
continue;
}else{
$new_array[$n[$arr[1]]] = $n[$arr[0]];
$output[] = $n;
}
}
return $output;
}