How to write database transactions in PHP

PHP is a widely used Web development language. Due to its simplicity, ease of learning, flexibility, and fast speed, it has become an important tool in the field of Web development. In web development, the database is one of the indispensable components. In order to ensure the integrity and consistency of the database, developers can use transactions to control database operations. This article will introduce how to write database transactions using PHP.

1. What is a database transaction?

Database Transaction refers to a set of database operations that can be processed as a single logical unit of work and satisfy the following four characteristics (ACID):

1. Atomic Atomicity: Transactions are indivisible units of operations that must be completed or rolled back.
2. Consistency: The state of the database should remain consistent before and after the transaction is executed.
3. Isolation: Modifications during transaction execution are not visible to other transactions.
4. Durability: After the transaction is successfully executed, the modifications to the database need to be permanently saved and will not be lost even if the system fails.

2. How does PHP implement database transactions?

Using PHP to implement database transactions requires the use of database operation extensions, such as MySQLi, PDO, etc. The following uses MySQLi as an example to introduce how to implement database transactions.

1. Start Transaction

Before using MySQLi for database operations, you need to create a MySQL connection first. After the connection is created, you can use the mysqli_begin_transaction() function to start a new transaction. The sample code is as follows:

$mysqli = new mysqli("localhost", "username", "password", "database");
$mysqli->begin_transaction();

2. Perform operations

After starting a transaction, you can perform database operations, such as inserting, updating, deleting data, etc. The sample code is as follows:

$mysqli->query("INSERT INTO `user` (`name`, `age`, `sex`) VALUES ('张三', 20, 1)");
$mysqli->query("UPDATE `user` SET `age` = 21 WHERE `name` = '张三'");
$mysqli->query("DELETE FROM `user` WHERE `name` = '李四'");

3. Commit or rollback the transaction

After the transaction operation is completed, you can use the mysqli_commit() function to commit the transaction and apply all operations to the database middle. If an error occurs or you want to rollback the operation, you can use the mysqli_rollback() function to implement transaction rollback. The sample code is as follows:

try {
    $mysqli->commit();
    echo "操作成功";
} catch (Exception $e) {
    $mysqli_rollback();
    echo "操作失败";
}

In the above code, if all operations are executed successfully, the transaction is committed and "operation successful" is output, otherwise the transaction is rolled back and "operation failed" is output.

3. Precautions for use

1. All database operations must be performed between the start of the transaction and commit or rollback.
2. During the transaction execution process, if an error occurs, the transaction must be rolled back in time to avoid irreversible damage to the database.
3. Wherever prepared statements can be used, try to use prepared statements to avoid the risk of SQL injection.
4. Each database connection can only conduct one transaction at the same time, and multiple transactions require multiple connections.
5. When using database transactions, you must ensure that all tables use the InnoDB storage engine, because InnoDB supports transactions, but MyISAM does not support transactions.

4. Summary

Using PHP to implement database transactions can effectively ensure the consistency and integrity of database operations and avoid adverse effects on the database. Developers can rationally use transaction operations based on specific business needs to improve application development efficiency and stability.

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