I have this code however, when the database already exists, I get an empty response and echo doesn't show anything:

try
{
    //die('here');

    $conn = new PDO("mysql:host=$host", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    if (!PDO_select_db($conn, $dbName)){
      echo "Database doesn't exist!";
      $sql = "CREATE DATABASE ".$dbName;
      if ($conn->query($sql) === TRUE) {
        echo "Database was created successfully";
      } else {
        echo "Error creating database: " . $conn->error;
      }

  } 
  else {
  echo "Database already exists!";
  }
}

What is wrong with this code?

As you see, using Firefox Inspect, in Network tab, I see No response data available for this request.

Expected behavior: since the database already exists, I am expecting to see Database already exists! in the Response section of Network tab.

So, my database, named judges, exists and using $ php -l submit.php I see that my code has no error. I can also see this in phpMyAdmin GUI:

CodePudding user response：

The easiest way to use a database in PDO is to name it in the DSN when you connect:

$conn = new PDO("mysql:host=$host;dbname=name_of_db", $username, $password);

If you want to change the default database, you can use PDO::exec() to run a USE <database> statement:

$conn->exec("USE name_of_db");

You can't use mysql_select_db() because all the mysql_* functions were deprecated in PHP 5.5 (circa 2013), and removed from PHP in version 7.0 (2015). You should use more current resources to learn PHP and PDO.

PS: Honestly, I don't add CREATE DATABASE to my application code. The database just better exist. If it doesn't, references to it will throw an exception, so I create the database manually before I deploy my application. Since that needs to happen only once, it's a waste of time and lines of code to check that the database exists during every PHP request.

CodePudding user response：

Turns out I am using a new version of PHP and the functions I was using were obsolete.

The code below works:

$host = "localhost";
$username = "root";
$password = "";
$dbName = "judges";

try
{

  $conn = new mysqli($host, $username, $password);
  if ($conn->connect_error) {
      die("Connection failed: " . $conn->connect_error);
  }

  // If database is not exist create one
  if (!mysqli_select_db($conn,$dbName)){
      $sql = "CREATE DATABASE ".$dbName;
      if ($conn->query($sql) === TRUE) {
          echo "Database created successfully";
      }else {
          echo "Error creating database: " . $conn->error;
      }
  } 


}
catch(PDOException $e)
{
    echo "in catch block";
    echo "Connection failed: " . $e->getMessage();
    echo $sql . "<br>" . $e->getMessage();
}