PDO freebsd找不到驱动程序

Question

I'm trying to connect on my database on Freebsd, php 56 using this code:

<?php
$host = "x";
$user  = "x";
$password =  "x";

try {
    $account = new PDO("mysql:host=$host;dbname=account", $user, $password);
} catch(PDOException $e) {
    die($e);
}

try {
    $player = new PDO("mysql:host=$host;dbname=player", $user, $password);
} catch(PDOException $e) {
    die($e);
}

and I'm getting this error

exception 'PDOException' with message 'could not find driver' in /usr/local/www/apache24/data/config/db.php:7 
Stack trace: 
#0 /usr/local/www/apache24/data/config/db.php(7): PDO->__construct('mysql:host=x', 'x', 'x') 
#1 /usr/local/www/apache24/data/index.php(3): include('/usr/local/www/...') 
#2 {main}

so I get that I should install the drivers. I didn't find anything useful on google for freebsd. Can you help me?