How do you handle errors and exceptions in PHP?

In PHP, errors and exceptions are used to handle unexpected situations that may occur during the execution of a script.

Errors are triggered when a non-recoverable situation occurs, such as a missing file or an undefined function. These can be handled using the set_error_handler() function, which allows you to specify a custom function to handle errors. For example:

Copy codefunction customErrorHandler($errno, $errstr, $errfile, $errline) {
    // log the error message and other details
    error_log("Error $errno: $errstr in $errfile on line $errline");
    // display a friendly error message to the user
    echo "Sorry, an error occurred. Our team has been notified.";
}
set_error_handler("customErrorHandler");

Exceptions, on the other hand, are thrown when a recoverable error occurs, such as a missing parameter or a failed validation. These can be handled using try-catch blocks. For example:

Copy codetry {
    // code that may throw an exception
    if (empty($_POST["username"])) {
        throw new Exception("Username is required.");
    }
} catch (Exception $e) {
    // log the exception message
    error_log($e->getMessage());
    // display a friendly error message to the user
    echo "Sorry, an error occurred. Our team has been notified.";
}

It is also possible to catch different types of exceptions using multiple catch blocks.

Copy codetry {
    // code that may throw an exception
    if (empty($_POST["username"])) {
        throw new Exception("Username is required.");
    }
    if (empty($_POST["password"])) {
        throw new Exception("Password is required.");
    }
} catch (Exception $e) {
    if ($e->getMessage() === "Username is required.") {
        // display a specific error message
        echo "Username is a required field";
    } else if ($e->getMessage() === "Password is required.") {
        // display a specific error message
        echo "Password is a required field";
    }else {
        // log the exception message
        error_log($e->getMessage());
        // display a friendly error message to the user
        echo "Sorry, an error occurred. Our team has been notified.";
    }
}

It’s also a good practice to use an exception handler function using set_exception_handler() function, that will handle all the uncaught exceptions.

In summary, handling errors and exceptions in PHP involves using set_error_handler() function to specify a custom function to handle errors, and using try-catch blocks to handle exceptions. It’s important to log the error message and other details, and display a friendly error message to the user.

Another way to handle exceptions in PHP is by using the finally block, which allows you to execute code regardless of whether an exception was thrown or not. This can be useful for cleaning up resources, such as closing database connections, or logging the success or failure of an operation. For example:

Copy codetry {
    // code that may throw an exception
    $db = new PDO("mysql:host=localhost;dbname=mydb", "user", "password");
    // perform database operations
    // ...
} catch (PDOException $e) {
    // log the exception message
    error_log($e->getMessage());
    // display a friendly error message to the user
    echo "Sorry, an error occurred. Our team has been notified.";
} finally {
    // close the database connection
    $db = null;
}

Another way to handle exception is by using the throw new Error(‘message’) , which throws an error exception, it’s a good way to raise an error when a function or method is called incorrectly.

In addition to using set_error_handler and try-catch blocks, you can also configure error reporting and logging settings in your PHP configuration file (php.ini) to control how errors and warnings are handled. You can set the error_reporting level to control which types of errors are reported, and you can set the error_log directive to specify a file where errors are logged.

In summary, handling errors and exceptions in PHP involves using set_error_handler() function to specify a custom function to handle errors, using try-catch blocks to handle exceptions, and the finally block to execute code regardless of whether an exception was thrown or not. It’s important to use the right function throw new Exception() or throw new Error() and to log the error message and other details, and display a friendly error message to the user.