What is mysql connection?

$ DbnewPDO () at the underlying layer, what is the DB instance generated? In linux, everything is a file. I think this instance should also be a file. 1. What information does this file store? Assume that the connection of {code...} DB is not active for a long time. mysql will change from... $ db = new PDO ()
What is the DB instance generated at the underlying layer?

In linux, everything is a file. I think this instance should also be a file.
1. What information does this file store?

Assume that:

$db = new PDO(...)while(true){sleep(90000)    $db->xx()}

If the DB connection is not active for a long time, mysql will be automatically disconnected. After the connection is closed, the PHP request will report the MySQL server has gone away error.

2. How can I determine whether the db is disconnected before $ DB-> xx?

Reply content:

$ Db = new PDO ()
What is the DB instance generated at the underlying layer?

In linux, everything is a file. I think this instance should also be a file.
1. What information does this file store?

Assume that:

$db = new PDO(...)while(true){sleep(90000)    $db->xx()}

If the DB connection is not active for a long time, mysql will be automatically disconnected. After the connection is closed, the PHP request will report the MySQL server has gone away error.

2. How can I determine whether the db is disconnected before $ DB-> xx?

1. What information does this file store?
   I didn't find the file. The instance objects are all in the memory.

2. How can I determine whether the db is disconnected before $ DB-> xx?
   You can throw exceptions:

  query('SELECT * from FOO') as $row) {        print_r($row);    }    $dbh = null;} catch (PDOException $e) {    print "Error!: " . $e->getMessage() . "
";    die();}?>

PHP provides persistent connections
Persistent connection cache can avoid the overhead of creating a new connection between each script and the database, so that the web application can be faster.

   true));?>

RESOURCE

Mysql causes two interactive_timeout and wait_timeout actions.
You can extend the time by modifying the mysql configuration file/etc/my. cnf. The value is set to 10 seconds.
[Mysqld]

wait_timeout=10interactive_timeout=10

Solution:
Change the two parameters:

wait_timeout=100interactive_timeout=100

After the MySQL Server is restarted, check that the settings have taken effect.
Try it

Essentially, the connection to mysql is a commonsocketSocket, so it is alsoFile Descriptor. Since YestcpLink, so both parties have the right to disconnect the link at any time.mysqlThe server defines the connection timeout time to prevent excessive connections.mysqlResource usage.

GenerallyphpNot RequiredsleepWhat?pdoThe use of objects does not require connection timeout,pdoWill maintain everything.

if($db){ $db->xx() }

For more information, see the official documentation.

Essentially a memory buffer