PDO Drivers in PHP

PDO Drivers

• PDO drivers provide support for basic database operations, including connecting to the database, executing SQL queries, retrieving data, and managing transactions.
• They may also provide additional features specific to the database system, such as stored procedures and user-defined functions.
• PDO drivers can help improve the security of PHP applications by providing support for prepared statements, which can prevent SQL injection attacks.

Prepared Statements

• Prepared statements are SQL queries that are precompiled by the database system and can be reused multiple times with different parameter values.
• They help to prevent SQL injection attacks by ensuring that user input is properly escaped and validated.

PDO Drivers and Database Systems

• Common PDO drivers include PDO MySQL, PDO PostgreSQL, PDO SQLite, PDO Oracle, and PDO Microsoft SQL Server.
• There are also many other PDO drivers available for less common database systems.
• PDO drivers provide a convenient and standardized way for PHP applications to interact with databases, regardless of the underlying database system.

Enabling PDO Driver

• To use PDO with a specific database, you need to install the corresponding PDO driver.
• After installing the PDO driver, you need to enable it in your PHP configuration by adding an extension directive to your php.ini file.

PDO Object and Database Connection

• After enabling the PDO driver, you can verify that PDO and the driver are working correctly by creating a PDO object and connecting to your database.
• The PDO object represents the database connection, and you can close the connection by setting the object to null.

DML Commands

• DML stands for Data Manipulation Language, which is a subset of SQL used to manipulate data stored in a database.
• The main DML commands are:
  • INSERT: used to insert new rows of data into a table.
  • UPDATE: used to modify existing data in a table.
  • DELETE: used to delete rows of data from a table.
  • SELECT: used to retrieve data from one or more tables.

Common PDO Errors

• SQLSTATE[HY 000]: occurs when the user is denied access to the database due to incorrect username or password, or lack of necessary privileges.
• Solution: check if the username and password are correct, and if the user has the necessary privileges to access the database.
• SQLSTATE[Integrity constraint violation]: occurs when trying to insert a record with a value that already exists in a unique or primary key column.
• Solution: update the existing record or modify the unique or primary key constraint to allow duplicate values.
• SQLSTATE[42 000]: occurs when there is a syntax error in the SQL query.
• Solution: review the query and check for any syntax errors, such as missing quotes or semicolons.
• SQLSTATE[HY 000]: occurs when the PDO driver cannot connect to the database server.
• Solution: check if the database server is running, and if the host, port, username, and password are correct.
• SQLSTATE[0 8004]: occurs when the maximum number of connections to the database has been reached.
• Solution: increase the maximum number of connections allowed or close unused connections.