Adding numbers from a MySQL column using PHP

First you need to connect to your database through the MySQLi extension, documentation here .

Once you've done this, simply run a query using the SUM () of MySQL:

$mysqli = new mysqli('localhost', 'usuario', 'senha', 'banco');
$mysqli->query('SELECT SUM(coluna) FROM tabela');

And to use the query result:

$resultado = $mysqli->fetch_assoc();

You're apparently using PDO , so here's an example:

$STH_SELECT = $dbh->query("SELECT sum(coluna_pra_somar) FROM catalogo_comment WHERE cm_item = '2'");
$totalSoma = $STH_SELECT->fetchColumn();