PHP Error Handling

Basic Error Handling: Using die() function

The die() function in PHP is a basic error handling in php that allows you to terminate the script execution and display a custom error message. It is primarily used for critical errors or situations where the script cannot continue executing.

The die() function takes a single argument, which is the error message to be displayed when the script terminates. This message can be a simple string or a more descriptive error message indicating the cause of the error.

Here's an example of using the die() function:

Explanation

In the example above, the script checks if a file exists using the file_exists() function. If the file does not exist, the die() function is called with a custom error message. The script execution terminates at that point, and the error message is displayed.

Defining Custom Error Handling Function

In PHP, you can define a custom error handling function to handle errors, warnings, and notices generated during the execution of your script. This allows you to have more control over how errors are handled and provides an opportunity to log, display, or handle errors in a way that suits your application's needs.

Syntax

The syntax of an error handling in PHP follows a specific format. When defining a custom error handling function, it should adhere to the following structure:

Parameters

When defining a custom error handling function in PHP, you can specify four parameters that are passed to the function when an error occurs. These parameters provide information about the error, allowing you to handle it accordingly. The parameters of the error handling function are as follows:

• Error Number ($errno): This parameter represents the level or type of the error that occurred. It is an integer value defined by PHP's error reporting system. Common error levels include E_ERROR, E_WARNING, E_NOTICE, E_PARSE, etc. You can use this parameter to determine the severity of the error and customize the error handling based on different error levels.
• Error Message ($errstr): This parameter contains the error message associated with the error. It provides a description of what went wrong. The error message helps you understand the cause of the error and can be used for logging purposes or displaying meaningful error messages to the user.

Possible Error levels

Error handling in php involves different error levels that categorize the severity of errors. These error levels are predefined constants that you can use to specify how errors should be reported, logged, or handled. The possible error levels in PHP include:

• E_ERROR: Indicates a fatal error that causes script termination. This error type signifies critical issues that prevent the script from executing further.
• E_WARNING: Represents non-fatal errors that don't halt the script but should be addressed. Warnings highlight potential issues that could affect the script's behavior.
• E_PARSE: Indicates parse errors that occur during script compilation. These errors occur when PHP encounters syntax errors or invalid code.
• E_NOTICE: Represents non-fatal errors that notify about potential problems or uninitialized variables. Notices help identify areas where code could be improved for better reliability.

set_error_handler() Function

The set_error_handler() function in PHP is used to set a user-defined error handler function. It allows you to define a custom function that will be called whenever an error occurs during the execution of your PHP script. This function gives you more control over how errors are handled, logged, or displayed, allowing you to tailor the error handling process to your specific requirements.

Here's the syntax for using the set_error_handler() function:

Example: Testing the Error Handler by Trying to Output Variable that Does not Exist

Here's an example that demonstrates testing the error handler by trying to output a variable that does not exist:

Explanation

In the above example, we first define a custom error handler function called customErrorHandler(). This function simply echoes the error message ($errstr) when an error occurs.

Next, we use the set_error_handler() function to set our custom error handler as the active error handler. Run the above code in your editor for a better and clear explanation.