What are the disadvantages of using persistent connection in PDO

Question

In PDO, a connection can be made persistent using the PDO::ATTR_PERSISTENT attribute. According to the php manual -

Persistent connectio

Answer 1

On my tests I had a connection time of over a second to my localhost, thus assuming I should use a persistent connection. Further tests showed it was a problem with 'localhost':

Test results in seconds (measured by php microtime):

• hosted web: connectDB: 0.0038912296295166
• localhost: connectDB: 1.0214691162109 (over one second: do not use localhost!)
• 127.0.0.1: connectDB: 0.00097203254699707

Interestingly: The following code is just as fast as using 127.0.0.1:

$host = gethostbyname('localhost');
// echo "
$host
";
$db = new PDO("mysql:host=$host;dbname=" . DATABASE . ';charset=utf8', $username, $password,
    array(PDO::ATTR_EMULATE_PREPARES => false,
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));