I have array of messages received from server, with key seen_by which contain users saw the message, it's structure :
[1] => Array
(
[seen_by] => Array
(
[1] => user_1
[2] => user_2
[3] => user_3
)
)
[2] => Array
(
[seen_by] => Array
(
[2] => user_2
[3] => user_3
)
)
[3] => Array
(
[seen_by] => Array
(
[3] => user_3
)
)
where they keys in seen_by array is user_id,
what i want to do is since user_2 already in the seen_by array of the second message ,so remove it from the first seen_by array , and since user_3 in seen_by array of third message , remove from the first two messages
I want to get array like
[1] => Array
(
[seen_by] => Array
(
[1] => user_1
)
)
[2] => Array
(
[seen_by] => Array
(
[2] => user_2
)
)
[3] => Array
(
[seen_by] => Array
(
[3] => user_3
)
)
CodePudding user response：
I've simplified the arrays for illustration but the idea is shown. You can loop through the arrays starting at the end and working backwards, removing elements that exist in later arrays.
$array = array(
array( 1, 2, 3 ),
array( 2, 3 ),
array( 3 ),
);
$len = count( $array );
for ( $i = $len -1 ; $i > 0; $i-- ) {
$curr_array = $array[ $i ];
for( $j = $i - 1; $j >= 0; $j-- ) {
$array[$j] = array_diff( $array[$j], $curr_array );
}
}
CodePudding user response：
Use foreach loop and loop from last to first. To do so, use array_reverse(). Use a $set to check if a user is already tracked using isset. If it is, unset it from the current subarray or add it to the $set and move with the next element. An array_reverse at the end is done again just to restore the original order.
Snippet:
<?php
function removeDups($data){
$set = [];
$res = [];
foreach(array_reverse($data) as &$sub){
foreach($sub['seen_by'] as $idx => $val){
if(isset($set[ $val ])){
unset($sub['seen_by'][ $idx ]);
}else{
$set[ $val ] = true;
}
}
$res[] = $sub;
}
return array_reverse($res);
}
print_r(removeDups($data));