Chapter 7: Error Handling and Exception Handling in PHP

In this chapter, we will explore error handling and exception handling in PHP. We will cover understanding different types of errors, handling errors using built-in error handling functions, and handling exceptions for more advanced error management.

7.1 Understanding errors in PHP:

PHP provides different types of errors, including syntax errors, runtime errors, and logical errors.

Syntax errors occur when there are mistakes in the code structure, such as missing parentheses or semicolons.

Runtime errors occur during the execution of the program, such as division by zero or accessing undefined variables.

Logical errors are bugs that result in incorrect program output or behavior.

7.2 Handling errors using built-in functions:

PHP provides built-in functions to handle errors and customize error reporting.

Functions like error_reporting(), ini_set(), and set_error_handler() help in managing error handling behavior.

Example:

php

""

<?php

   // Displaying all types of errors

   error_reporting(E_ALL);

   

   // Enabling error display

   ini_set('display_errors', 1);

   

   // Custom error handler

   function customErrorHandler($errno, $errstr, $errfile, $errline) {

       echo "Error: $errstr";

   }

   set_error_handler("customErrorHandler");

   

   // Triggering an error

   echo $undefinedVariable;

?>

7.3 Exception handling:

Exceptions provide a more advanced error handling mechanism in PHP.

We can use the try, catch, and finally blocks to handle exceptions.

The throw statement is used to throw an exception when an error or exceptional condition occurs.

Example:

php

""

<?php

   // Custom exception class

   class CustomException extends Exception {

       public function __toString() {

           return "Custom Exception: " . $this->getMessage();

       }

   }

   

   // Exception handling

   try {

       throw new CustomException("An error occurred.");

   } catch (CustomException $e) {

       echo $e; // Output: Custom Exception: An error occurred.

   } finally {

       echo "Finally block executed.";

   }

?>

7.4 Logging errors:

Logging errors helps in tracking and troubleshooting issues in a production environment.

We can use functions like error_log() or logging libraries to write error messages to log files.

Example:

php

""

<?php

   // Logging errors to a file

   $errorMessage = "An error occurred.";

   error_log($errorMessage, 3, "error.log");

?>

By following the explanations and examples in this chapter, you will gain a solid understanding of error handling and exception handling in PHP, allowing you to effectively manage and handle errors, both through built-in functions and custom exception handling.