How to Group Rows in a 2D Array by a Column and Sum Another Column in PHP?

Grouping 2D Array Rows by a Column and Summing Another Column

To group rows in a 2D array based on a specific column and sum another column, you can employ the following approach:

Suppose we have an array like this:

<code class="php">[
    ['url_id' => 2191238, 'time_spent' => 41],
    ['url_id' => 2191606, 'time_spent' => 215],
    ['url_id' => 2191606, 'time_spent' => 25]
]</code>

To calculate the sum of time_spent values for each unique url_id, we can use the following PHP code:

<code class="php">$ts_by_url = array();
foreach($array as $data) {
    if(!array_key_exists($data['url_id'], $ts_by_url))
        $ts_by_url[ $data['url_id'] ] = 0;
    $ts_by_url[ $data['url_id'] ] += $data['time_spent'];
}</code>

In this code, we loop through the array and create an array ($ts_by_url) that is indexed by url_id. For each data item in the loop, we check if its url_id exists in $ts_by_url. If it does not, we set its value to 0. Then, we increment the time_spent value by the time_spent in the current data item.

After the loop finishes, $ts_by_url will contain the desired results:

2191238 => 41
2191606 => 240 // == 215 + 25

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