php - pdo向数据库插入数据失败？

Question

错误代码：

SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'insert into admin (userid,password,collection) values ('John', 'Doe', 'jo')' at line 1

pdo代码：

$servername="localhost";
$user="root";
$psw="444444";
try{
            
            
            $con=new PDO("mysql:host=$servername;dbname:mydb",$user,$psw);
            $con->query("set names utf8");
            $con->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

            
            if($con){
                
                $sql="use mydb insert into admin (userid,password,collection) values ('John', 'Doe', 'jo')";
                $con->exec($sql);

            }
            }
            catch(PDOException $e)
            {
                echo  $e->getMessage();
            }

报错信息说我sql有语法错误，但是我的sql语句在mysql执行时是可以插入数据的，而且有插入权限，请问为什么这里出错了？

Answer 1

use mydbAdd a semicolon after it, because these are two sentences of sql

Answer 2

You have already specified the database when connecting, so there is no needuse mydb.

Answer 3

Is it because the symbols are not used well? Try this:
$sql='use mydb insert into admin ("userid","password","collection") values ​​("John", "Doe", "jo" )';

Answer 4

use mydb does not need to be specified every time, just specify it once, and then SQL