Set_error_handler function in PHP - Mini Project: Build & Apply

Using set_error_handler in PHP

📖 Scenario: Imagine you are building a PHP script that needs to handle errors in a custom way. Instead of PHP showing default error messages, you want to catch errors and display a friendly message or log them differently.

🎯 Goal: You will create a custom error handler function and use set_error_handler to tell PHP to use your function when an error happens.

📋 What You'll Learn

Create a custom error handler function named myErrorHandler that accepts the standard error parameters.

Use set_error_handler to set myErrorHandler as the active error handler.

Trigger a warning error using trigger_error to test the custom handler.

Print the custom error message from inside the error handler.

💡 Why This Matters

🌍 Real World

Custom error handlers help websites and applications show friendly messages or log errors in a controlled way instead of default PHP errors.

💼 Career

Knowing how to manage errors is important for PHP developers to build robust, user-friendly applications and maintain code quality.

1

Create the custom error handler function

Write a function called myErrorHandler that accepts four parameters: $errno, $errstr, $errfile, and $errline. Inside the function, use echo to print the string: "Custom error: " followed by the error message $errstr and a newline character.

PHP

# Write the function myErrorHandler with parameters $errno, $errstr, $errfile, $errline
# Inside, print "Custom error: " followed by $errstr and a newline

Need a hint?

Define a function named myErrorHandler with the four error parameters. Use echo to print the message.

2

Set the custom error handler

Use set_error_handler to set myErrorHandler as the active error handler.

PHP

<?php
function myErrorHandler($errno, $errstr, $errfile, $errline) {
    echo "Custom error: $errstr\n";
}

# Use set_error_handler to set myErrorHandler as the error handler

Need a hint?

Call set_error_handler with the string 'myErrorHandler' as argument.

3

Trigger a warning error

Use trigger_error to trigger a user warning with the message 'This is a test warning.'.

PHP

<?php
function myErrorHandler($errno, $errstr, $errfile, $errline) {
    echo "Custom error: $errstr\n";
}

set_error_handler('myErrorHandler');

# Trigger a warning error with message 'This is a test warning.'

Need a hint?

Call trigger_error with the message and E_USER_WARNING as parameters.

4

Print the custom error message

Run the script and observe that the output shows the custom error message starting with Custom error: This is a test warning.

PHP

<?php
function myErrorHandler($errno, $errstr, $errfile, $errline) {
    echo "Custom error: $errstr\n";
}

set_error_handler('myErrorHandler');

trigger_error('This is a test warning.', E_USER_WARNING);

# Run the script to see the output

Need a hint?

Run the PHP script. The output should show the custom error message.