Remove duplicates from multidimensional associative array in php if two values match

Question

I have a multidimensional array of the following structure and I want to remove duplicates from it. For example if the ["amount"] is the same for two ["cities"] but the ["time"] is the same or different then I count this is a duplicate and want to remove this node from the array.

In the following example I want to remove completely node 0 from the array as the city and amount are the same as node 1. They are both Bristol (Bristol, United Kingdom) and 373 Even though the time is different being 17:15 and 17:16.

If the times are different as in this case then I would remove the later time.

array(8) {
  [0]=>
  array(3) {
    ["time"]=>
    string(5) "17:16"
    ["city"]=>
    string(33) "Bristol (Bristol, United Kingdom)"
    ["amount"]=>
    int(373)
  }
  [1]=>
  array(3) {
    ["time"]=>
    string(5) "17:15"
    ["city"]=>
    string(33) "Bristol (Bristol, United Kingdom)"
    ["amount"]=>
    int(373)
  }
  [2]=>
  array(3) {
    ["time"]=>
    string(5) "17:16"
    ["city"]=>
    string(37) "Wednesbury (Sandwell, United Kingdom)"
    ["amount"]=>
    int(699)
  }
  [3]=>
  array(3) {
    ["time"]=>
    string(5) "17:16"
    ["city"]=>
    string(45) "Wolverhampton (Wolverhampton, United Kingdom)"
    ["amount"]=>
    int(412)
  }
  [4]=>
  array(3) {
    ["time"]=>
    string(5) "17:15"
    ["city"]=>
    string(33) "Swansea (Swansea, United Kingdom)"
    ["amount"]=>
    int(249)
  }
  [5]=>
  array(3) {
    ["time"]=>
    string(5) "17:16"
    ["city"]=>
    string(39) "Watford (Hertfordshire, United Kingdom)"
    ["amount"]=>
    int(229)
  }
  [6]=>
  array(3) {
    ["time"]=>
    string(5) "17:14"
    ["city"]=>
    string(39) "Nottingham (Nottingham, United Kingdom)"
    ["amount"]=>
    int(139)
  }
  [7]=>
  array(3) {
    ["time"]=>
    string(5) "17:13"
    ["city"]=>
    string(31) "Dartford (Kent, United Kingdom)"
    ["amount"]=>
    int(103)
  }
}

Answer 1

<?php

$data = array(
    array(
        'time' => '17:16',
        'city' => 'Bristol',
        'amount' => 373,
    ),
    array(
        'time' => '18:16',
        'city' => 'Bristol',
        'amount' => 373,
    ),
    array(
        'time' => '18:16',
        'city' => 'Wednesbury',
        'amount' => 699,
    ),
    array(
        'time' => '19:16',
        'city' => 'Wednesbury',
        'amount' => 699,
    ),
);

$tmp = array();
foreach ($data as $row) {
    $city   = $row['city'];
    $amount = $row['amount'];

    if (!isset($tmp[$city][$amount]) 
        || $tmp[$city][$amount]['time'] < $row['time']) {
        $tmp[$city][$amount] = $row;
    }
}

$data = array();

foreach ($tmp as $cities) {
    foreach ($cities as $city) {
        $data[] = $city;
    }
}

var_dump($data);