PHP exception handling: how to use the try-catch-finally statement

In PHP, the try-catch-finally statement is used for exception handling, which enhances the robustness of the application by protecting code blocks and providing exception handling and cleanup mechanisms.

PHP exception handling: use try-catch-finally statement

In PHP, exception handling is a key mechanism, use Used to manage unexpected events and errors, making your applications more robust and reliable. This article will guide you in using the try-catch-finally statement to handle exceptions.

try-catch-finally statement

The try-catch-finally statement is used to place a block of code in a controlled exception handling environment. The syntax is as follows:

try {
  // 受保护的代码块
} catch (Exception $e) {
  // 异常处理代码
} finally {
  // 无论是否发生异常，都会执行的代码
}

Practical case: Database connection exception

Suppose we have a function that connects to the database, but there are potential errors:

function connectToDatabase() {
  $connection = new mysqli("localhost", "username", "password", "database");

  if ($connection->connect_errno) {
    throw new Exception("数据库连接失败: " . $connection->connect_error);
  }

  return $connection;
}

We can use the try-catch-finally statement to handle database connection exceptions:

try {
  $connection = connectToDatabase();

  // 使用数据库连接
} catch (Exception $e) {
  echo "数据库连接失败: " . $e->getMessage();
} finally {
  // 始终关闭数据库连接
  if (isset($connection)) {
    $connection->close();
  }
}

In the finally block, we ensure that the database connection is closed even when an exception occurs.

Best Practice

• Catch only known exception types: Do not catch the base class Exception, but catch the specific exception type (e.g. mysqli_sql_exception).
• Provide a meaningful error message: Include enough information in the exception message to help you debug and solve the problem.
• Use the finally block to clean up resources: Always release allocated resources (such as database connections, file handles) regardless of whether an exception occurs.
• Don't abuse exception handling: Only use exception handling to handle truly unexpected errors, not for flow control.

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