In PHP development, catch exceptions and customize exception classes to improve code robustness. 1. Use try to wrap error codes, catch catch and handle exceptions, throw throw exceptions manually; 2. Custom exception classes inherit Exceptions, such as DatabaseException, PermissionException, and targeted processing; 3. Get detailed error information through getMessage(), getCode(), getFile() and other methods for debugging, but the production environment needs to turn off sensitive output.

In PHP development, exception handling is an important part of building robust applications. Simply put, an exception is an error or unexpected behavior that occurs during the program's operation. By catching and handling these exceptions, program crashes can be avoided and clearer error feedback can be provided. Custom exceptions can help us better organize code structure and distinguish different types of errors.

Basic exception catching method

In PHP, try...catch structure is used to catch exceptions. The basic idea is: put the code that may make errors in try block, and once an exception is thrown, it will be caught by catch block immediately following it.

 try {
    // Code that may throw an exception throw new Exception("Error");
} catch (Exception $e) {
    //Catch and handle exception echo "Catched exception:" . $e->getMessage();
}

The key point here is:

• throw is used to manually throw an exception.
• The type in brackets after catch determines which exceptions it can catch.
• Exception is a basic exception class built in PHP.

Note that if you are not sure what type of exception will be thrown, you can also use multiple catch blocks to handle different exception types separately.

Create a custom exception class

Although the built-in Exception class can meet most needs, in actual projects, we often need to define different exception types according to business logic. For example, database operation failed, insufficient permissions, errors in parameters, etc.

Custom exception class only needs to inherit PHP's Exception class:

 class DatabaseException extends Exception {}
class PermissionException extends Exception {}

This way, error types can be more explicitly identified when thrown or captured:

 try {
    if (!connectToDatabase()) {
        throw new DatabaseException("Database connection failed");
    }
} catch (DatabaseException $e) {
    echo "Database Exception:" . $e->getMessage();
} catch (Exception $e) {
    echo "Unknown exception:" . $e->getMessage();
}

There are several benefits to doing this:

• Improve code readability and see the exception type at a glance.
• It is easier to do targeted processing, such as recording logs and returning specific response codes.
• It is conducive to teamwork and unifies exception naming rules.

Detailed output and debugging of exception information

When an exception occurs, in addition to obtaining simple error information, you can also access more details to help troubleshoot problems.

Several commonly used methods include:

• $e->getMessage() : Get the error description
• $e->getCode() : Get the error code
• $e->getFile() and $e->getLine() : locate the file and line number of the error occurred
• $e->getTrace() or $e->__toString() : Get the complete call stack information

For example:

 catch (Exception $e) {
    echo "Error message:" . $e->getMessage() . "<br>";
    echo "Error location:" . $e->getFile() . "Thread" . $e->getLine() . "Line<br>";
    echo "<pre class="brush:php;toolbar:false">" . $e->getTraceAsString() . "

This information is very useful during the debugging phase. But it should be noted that detailed error output should be turned off in production environments to avoid exposing sensitive information.

Basically that's it. Exception handling is not a complex mechanism, but it is easily overlooked or used in irregular terms. The rational use of built-in and custom exceptions can make your PHP applications more maintainable and fault-tolerant.

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