What is the right way or how to close persistent PDO connections in PHP?

Question

I need to close the connection to the Mysql database in PHP in the code below:

try {
  $conn = new PDO('mysql:host=localhost;dbname=banco', "root", "", array(PDO::ATTR_PERSISTENT => true));
  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e) {
  echo 'ERROR: ' . $e->getMessage();
}
//tenta fechar a conexao
$conn = null;

I need to close the persistent connection to a Mysql database in PHP. I tried to close the connection by setting the variable $conn as null, but it doesn’t seem to be working.

When I use the command SHOW STATUS WHERE variable_name = 'Threads_connected'; in Mysql to check the active connections they do not decrease, but work when the connection is not persistent and Seto the variable $conn as null.

Someone could help me?

Answer 1

Answering your question, according to the documentation here: https://www.php.net/manual/en/pdo.connections.php

Persistent Connections are not closed at the end of the script, but are cached and re-used when Another script requests a Connection using the same credentials. The persistent Connection cache Allows you to avoid the overhead of establishing a new Connection Every time a script needs to talk to a database, Resulting in a Faster web application.

That is to say, "Persistent connections are not closed at the end of the script, they are cached to be reused".

When setting the connection object to null ($conn = null) releases the object to be destroyed and the connection to be closed. If you want the connection closed at this point, don’t use a persistent connection, because that’s exactly the opposite of your purpose.

The purpose of a persistent connection is to remain open to avoid the overhead to redo the connection.