How do I make a query using PDO? - php

Question

I am trying to make this query using PDO and it is returning and error.I have already verified the connection to the database.
function temperaturaMedia($data_inicio,$data_final,$ema)
{
$db = 'sensorzapp_db';
$query = "SELECT
DATE(DTM) AS 'Dia',
ROUND(AVG(TMP),1) AS 'Temp. Med.'
FROM dados_meteo
WHERE POM = '$ema'
AND DATE(DTM) BETWEEN '$data_inicio' AND '$data_final'
GROUP BY DATE(DTM)";
$stmt = $db->query($query);
return $stmt->fetchAll(PDO::FETCH_ASSOC);
}

Answer 1

You are trying to execute a query on a string, you need to connect to the database, like this:
function temperaturaMedia($data_inicio,$data_final,$ema)
{
try {
$db = new PDO("mysql:host=localhost;dbname=sensorzapp_db","user","password");
} catch($ex) { die("Connection failed"); } // To not disclosure username & password when connection fails (look at the red box on http://www.php.net/manual/de/pdo.connections.php)
$query = "SELECT
DATE(DTM) AS 'Dia',
ROUND(AVG(TMP),1) AS 'Temp. Med.'
FROM dados_meteo
WHERE POM = '$ema'
AND DATE(DTM) BETWEEN '$data_inicio' AND '$data_final'
GROUP BY DATE(DTM)";
$stmt = $db->query($query);
return $stmt->fetchAll(PDO::FETCH_ASSOC);
}