Error handling in PHP is crucial for managing and responding to errors that occur during the execution of your script. PHP offers various mechanisms to handle errors, ranging from simple error reporting to more advanced error handling techniques.

Types of Errors in PHP

1. Syntax Errors: Errors in the code syntax, usually detected by the PHP parser before execution.
2. Runtime Errors: Errors that occur during the execution of the script, such as division by zero or trying to access a file that doesn't exist.
3. Logical Errors: Errors in the program logic that cause unexpected results but don’t produce PHP errors.
4. Warnings and Notices: Non-fatal errors or issues that do not stop script execution but indicate potential problems.

Error Reporting

To control the level of error reporting in PHP, use the error_reporting() function and configure error reporting in php.ini.

Example:

<?php
error_reporting(E_ALL); // Report all types of errors
ini_set('display_errors', 1); // Display errors on the screen
?>

Error Levels:

• E_ERROR - Fatal run-time errors.
• E_WARNING - Run-time warnings (non-fatal errors).
• E_PARSE - Compile-time parse errors.
• E_NOTICE - Run-time notices (minor errors).
• E_ALL - All errors and warnings (recommended for development).

Custom Error Handling

You can define a custom error handler using the set_error_handler() function. This allows you to handle errors in a more controlled manner, such as logging errors or displaying user-friendly messages.

Example:

<?php
function customError($errno, $errstr, $errfile, $errline) {
    echo "<b>Error:</b> [$errno] $errstr<br>";
    echo " Error on line $errline in $errfile<br>";
    // Log error to a file or database
}

// Set the custom error handler
set_error_handler("customError");

// Trigger an error
echo $undefined_variable;
?>

Exception Handling

Exceptions are a way to handle errors in a more structured way. Use the try, catch, and finally blocks to manage exceptions.

Example:

<?php
class CustomException extends Exception {
    public function errorMessage() {
        return "Error occurred: " . $this->getMessage();
    }
}

try {
    // Code that may throw an exception
    if (!file_exists("example.txt")) {
        throw new CustomException("File not found.");
    }
} catch (CustomException $e) {
    echo $e->errorMessage();
} finally {
    echo "Execution completed.";
}
?>

Error Logging

Logging errors helps in troubleshooting and debugging. You can configure PHP to log errors to a file or send them to a system log.

Configuration in php.ini:

log_errors = On
error_log = /path/to/php-error.log

Example:

<?php
// Log an error message
error_log("This is an error message", 3, "/path/to/php-error.log");
?>

Handling Errors in PHP with Modern Practices

1. Error Reporting Configuration: Use php.ini or runtime configuration to set appropriate error reporting levels.
2. Custom Error Handlers: Implement custom error handlers to manage errors effectively.
3. Exception Handling: Use exceptions for handling errors in object-oriented programming and complex scenarios.
4. Error Logging: Configure and use error logging for better debugging and monitoring.
5. User-Friendly Error Messages: Avoid displaying raw error messages to users; instead, show user-friendly messages and log detailed errors for developers.