PHP – remove duplicate indexes from array, compared by one of it values

I have a PHP array with indexes, its values can be duplicated. I want to remove all duplicated indexes from this array:

array(3) {
  [0]=>
  array(5) {
    ["uid"]=>
    int(1)
    ["title"]=>
    string(26) "Title A"
    ["tstamp"]=>
    string(10) "1580296755"
  }
  [1]=>    // <----- should be removed, because it's tstamp is lower than it's duplicate
  array(5) {
    ["uid"]=>
    int(2)
    ["title"]=>
    string(33) "Title B"   // <----- duplicate value
    ["tstamp"]=>
    string(10) "1580296797"
  }
  [2]=>
  array(5) {
    ["uid"]=>
    int(3)
    ["title"]=>
    string(33) "Title B"   // <----- duplicate value
    ["tstamp"]=>
    string(10) "1580298366"
  }
}

So, Index 1 and 2 with the same title “Title B” are duplicated. Only the one with the higher tstamp should be exists, all older ones with same title should be removed from array:

array(3) {
  [0]=>
  array(5) {
    ["uid"]=>
    int(1)
    ["title"]=>
    string(26) "Title A"
    ["tstamp"]=>
    string(10) "1580296755"
  }
  [1]=>
  array(5) {
    ["uid"]=>
    int(3)
    ["title"]=>
    string(33) "Title B"
    ["tstamp"]=>
    string(10) "1580298366"
  }
}

Hope someone understand me and can help to solve my problem.

Answer

Just create an empty array, loop through your old array and add them to the new array with the key as the title.

<?php

$old = [
    ['uid' => 1, 'title' => 'Title A', 'tstamp' => 1580296755],
    ['uid' => 2, 'title' => 'Title B', 'tstamp' => 1580296797],
    ['uid' => 3, 'title' => 'Title B', 'tstamp' => 1580298366],
];

$new = [];
foreach($old as $row) {

    $title = $row['title'];

    //check if title exists as key of `$new` array.
    //if it does exist as a key, check if `tstamp` in the loop is higher than the existing record
    if(!array_key_exists($title, $new) || ($new[$title]['tstamp'] < $row['tstamp'])) {

        //update or insert record if the if-statement evaluates to true
        $new[$title] = $row;
    }
}

Output:

Array
(
    [Title A] => Array
        (
            [uid] => 1
            [title] => Title A
            [tstamp] => 1580296755
        )

    [Title B] => Array
        (
            [uid] => 3
            [title] => Title B
            [tstamp] => 1580298366
        )

)

This has the added benefit of being able to select titles easier, for example $new['Title A']. If you want the key indexes to still be numerical, you can use $new = array_values($new); to do so. If you use array_values(), the output matches your expected output exactly.