I want to create a class which uses PDO to interact with MySQL. Can I create a new MySQL table using PDO?
Yes, you can.
The dsn part, which is the first parameter of the PDO constructor, does not have to have a database name. You can simply use mysql:host=localhost. Then, given you have the right privilege, you can use regular SQL commands to create a database and users, etc.
Following is an example from an install.php file. It logs in with root, create a database, a user, and grant the user all privilege to the new created database:
<?php
$host = "localhost";
$root = "root";
$root_password = "rootpass";
$user = 'newuser';
$pass = 'newpass';
$db = "newdb";
try {
$dbh = new PDO("mysql:host=$host", $root, $root_password);
$dbh->exec("CREATE DATABASE `$db`;
CREATE USER '$user'#'localhost' IDENTIFIED BY '$pass';
GRANT ALL ON `$db`.* TO '$user'#'localhost';
FLUSH PRIVILEGES;")
or die(print_r($dbh->errorInfo(), true));
}
catch (PDOException $e) {
die("DB ERROR: " . $e->getMessage());
}
?>
Yes, it's the same, like running a regular query like "CREATE TABLE ...".
Related
I am trying to connect to the database via PDO and my db.php file is as follows:
$host = "localhost";
$db = "mydb";
$user = "user";
$pass = "qRES2fIWK8Gg";
try
{
$db = new PDO("mysql:host = $host; dbname = $db", $user, $pass);
$db -> exec ("SET NAMES utf8"); // charset = utf8 doesn't work.
echo "Database connection is successful. <br>";
}
catch (PDOException $e)
{
echo $e -> getMessage();
}
I have two problems which I think there is a connection between them.
When I check the db.php, I can get Database connection is successful message even though I change the host and dbname with random and incorrect values. How is that possible? When I try the same process on the database username and password, it gives an error.
I am unable to run SQL queries without stating database name in it as PDO
doesn't fetch database name from db.php. For example, this SQL query
doesn't work:
SELECT * FROM settings WHERE settings_id= :id
However, this one works successfully:
SELECT * FROM mydb.settings WHERE settings_id= :id
I was working on localhost. After this problem, I thought it has been related to localhost and I moved my project to a virtual host. However, this step hasn't fixed the problems.
Removing the spaces in your DSN string should resolve your issues:
"mysql:host=$host;dbname=$db"
How can I perform a SQLite3 exec at the same time in PHP?
I have this code (by example):
$bd = new SQLite3("database.db");
$bd->busyTimeout(5000);
$bd->exec("INSERT into 'foo' ('data') values ('bar')");
$bd->close();
unset($bd);
And it works, but the real problem is when I connect another computer to my server and I made the insert at the same time (really, I press the key that trigger the code at the same time in both computers) and it show an error "database is locked".
I know that with the pragma WAL the database works in multithread, but it even show the error. Thank you a lot! and sorry for my bad english.
The problem is sqlite3 employs database locking, as opposed to row or column locking like mysql or postgresql. If you want to do two things at the same time try using mysql, or postgresql. In mysql you would have to create the database. Your code would then look something like this:
$servername = "localhost";
$username = "username";
$password = "password";
try {
$conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
echo "Connected successfully";
}
catch(PDOException $e)
{
echo "Connection failed: " . $e->getMessage();
}
$count = $conn->exec("INSERT into 'foo' ('data') values ('bar')");
$conn = null // close connection
I want to select a MySQL database to use after a PHP PDO object has already been created. How do I do this?
// create PDO object and connect to MySQL
$dbh = new PDO( 'mysql:host=localhost;', 'name', 'pass' );
// create a database named 'database_name'
// select the database we just created ( this does not work )
$dbh->select_db( 'database_name' );
Is there a PDO equivalent to mysqli::select_db?
Perhaps I'm trying to use PDO improperly? Please help or explain.
EDIT
Should I not be using PDO to create new databases? I understand that the majority of benefits from using PDO are lost on a rarely used operation that does not insert data like CREATE DATABASE, but it seems strange to have to use a different connection to create the database, then create a PDO connection to make other calls.
Typically you would specify the database in the DSN when you connect. But if you're creating a new database, obviously you can't specify that database the DSN before you create it.
You can change your default database with the USE statement:
$dbh = new PDO("mysql:host=...;dbname=mysql", ...);
$dbh->query("create database newdatabase");
$dbh->query("use newdatabase");
Subsequent CREATE TABLE statements will be created in your newdatabase.
Re comment from #Mike:
When you switch databases like that it appears to force PDO to emulate prepared statements. Setting PDO::ATTR_EMULATE_PREPARES to false and then trying to use another database will fail.
I just did some tests and I don't see that happening. Changing the database only happens on the server, and it does not change anything about PDO's configuration in the client. Here's an example:
<?php
// connect to database
try {
$pdo = new PDO('mysql:host=huey;dbname=test', 'root', 'root');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
} catch(PDOException $err) {
die($err->getMessage());
}
$stmt = $pdo->prepare("select * from foo WHERE i = :i");
$result = $stmt->execute(array("i"=>123));
print_r($stmt->fetchAll(PDO::FETCH_ASSOC));
$pdo->exec("use test2");
$stmt = $pdo->prepare("select * from foo2 WHERE i = :i AND i = :i");
$result = $stmt->execute(array("i"=>456));
print_r($stmt->fetchAll(PDO::FETCH_ASSOC));
If what you're saying is true, then this should work without error. PDO can use a given named parameter more than once only if PDO::ATTR_EMULATE_PREPARES is true. So if you're saying that this attribute is set to true as a side effect of changing databases, then it should work.
But it doesn't work -- it gets an error "Invalid parameter number" which indicates that non-emulated prepared statements remains in effect.
You should be setting the database when you create the PDO object. An example (from here)
<?php
$hostname = "localhost";
$username = "your_username";
$password = "your_password";
try {
$dbh = new PDO("mysql:host=$hostname;dbname=mysql", $username, $password);
echo "Connected to database"; // check for connection
}
catch(PDOException $e)
{
echo $e->getMessage();
}
?>
Alternatively, you can select a MySQL database to use after a PHP PDO object has already been created as below:
With USE STATEMENT. But remember here USE STATEMENT is mysql command
try
{
$conn = new PDO("mysql:host=$servername;", $username, $password);
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$conn->exec("use databasename");
//application logic
}
catch(PDOException $e)
{
echo $sql . "<br>" . $e->getMessage();
}
$conn = null;
I hope my code is helpful for requested
As far as I know, you have to create a new object for each connection. You can always extend the PDO class with a method which connects to multiple databases. And then use it as you like:
public function pickDatabase($db) {
if($db == 'main') {
return $this->db['main']; //instance of PDO object
else
return $this->db['secondary']; //another instance of PDO object
}
and use it like $yourclass->pickDatabase('main')->fetchAll('your stuff');
Would it be possible to have more than one databases to be connected in only one index.php, just like in a blog site where we will have different database for users information and another database for the blog information from the user?
$con=mysql_connect('host1', 'user1', 'password1');
mysql_select_db('db1',$con);
Pay attention to write function
Just use
mysqlconnect('host1', 'user1', 'password1');
mysql_select_db('db1');
to select diferent databases from the same server.
Although it is quite possible, it would make very little sense to split users and blog entries between separate databases.
If you are doing it for some reason, you better revise your architecture.
May be you are confusing a database and a table?
Assuming you mean you want to connect to one database server, with multiple databases, just reference the database name with the table name. You "select" one database as your default, when you need to reference a table from another database, prepend the database name. For example, if your default database is the blog, you can query the user database like this:
SELECT * FROM users.user_table;
Maybe you should try using PDO.
Although it makes a little sense to split compact data (users + blog posts) into several databases, because you won't be able to use JOIN or FOREIGN KEY, but let's imagine you have situation where you need to sync your local user database with main blog database:
// Establish first connection
$dsn1 = 'mysql:dbname=testdb;host=127.0.0.1';
$user1 = 'dbuser';
$password1 = 'dbpass';
try {
$dbh1 = new PDO($dsn1, $user1, $password1);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
$dsn2 = 'mysql:dbname=testdb;host=1.2.3.4';
$user2 = 'dbuser2';
$password2 = 'dbpass2';
try {
$dbh2 = new PDO($dsn2, $user2, $password2);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
foreach ($dbh1->query('SELECT ...') as $row) {
$dbh2->query( 'INSERT INTO...');
}
I've made a database using phpMyAdmin , now I want to make a register form for my site where peaple can register .I know how to work with input tags in HTML and I know how to insert data into a database but my problem is that I don't know how I can connect to the database that is already made in phpMyAdmin.
The database is a MySQL database, not a phpMyAdmin database. phpMyAdmin is only PHP code that connects to the DB.
mysql_connect('localhost', 'username', 'password') or die (mysql_error());
mysql_select_database('db_name') or die (mysql_error());
// now you are connected
Connect to MySQL
<?php
/*** mysql hostname ***/
$hostname = 'localhost';
/*** mysql username ***/
$username = 'username';
/*** mysql password ***/
$password = 'password';
try {
$dbh = new PDO("mysql:host=$hostname;dbname=mysql", $username, $password);
/*** echo a message saying we have connected ***/
echo 'Connected to database';
}
catch(PDOException $e)
{
echo $e->getMessage();
}
?>
Also mysqli_connect() function to open a new connection to the MySQL server.
<?php
// Create connection
$con=mysqli_connect(host,username,password,dbname);
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
?>
Set up a user, a host the user is allowed to talk to MySQL by using (e.g. localhost), grant that user adequate permissions to do what they need with the database .. and presto.
The user will need basic CRUD privileges to start, that's sufficient to store data received from a form. The rest of the permissions are self explanatory, i.e. permission to alter tables, etc. Give the user no more, no less power than it needs to do its work.
This (mysql_connect, mysql_...) extension is deprecated as of PHP 5.5.0, and will be removed in the future. Instead, the MySQLi or PDO_MySQL extension should be used. (ref: http://php.net/manual/en/function.mysql-connect.php)
Object Oriented:
$mysqli = new mysqli("host", "user", "password");
$mysqli->select_db("db");
Procedural:
$link = mysqli_connect("host","user","password") or die(mysqli_error($link));
mysqli_select_db($link, "db");
$db = new mysqli('Server_Name', 'Name', 'password', 'database_name');