Error Handling and Exception Handling in PHP: Best Practices 🚀

Errors happen! But instead of displaying ugly PHP error messages on a live site, we need to handle them gracefully.

🎯 In this guide, you’ll learn:

✅ Different types of PHP errors
✅ How to use error reporting levels
✅ Handling errors with try...catch blocks
✅ Logging errors instead of displaying them
✅ Building a custom error handler
✅ A real-world error-handling mini project

Let’s fix those errors like a pro! 🚀

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1️⃣ Types of Errors in PHP

PHP has three major types of errors:

Error Type	Description
Notices	Minor issues (e.g., using an undefined variable).
Warnings	More serious but the script continues (e.g., file not found).
Fatal Errors	Critical errors that stop execution (e.g., calling a missing function).

🔥 Example: Understanding PHP Errors

<?php
echo $undefined_var; // Notice: Undefined variable

include("missing_file.php"); // Warning: File not found

non_existent_function(); // Fatal Error: Function does not exist
?>

💡 We need proper error handling to prevent these from breaking our app!

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2️⃣ Enabling Error Reporting for Development

🔹 To see all errors and warnings, enable full error reporting in development mode.

Add this to your PHP script:

error_reporting(E_ALL);
ini_set("display_errors", 1);

🔥 Why use this?
✅ Helps debug issues faster.
✅ Shows all errors and warnings.

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3️⃣ Handling Errors with try...catch

💡 Exceptions allow you to catch and handle errors instead of stopping execution.

Example: Handling Errors Gracefully

<?php
function divide($a, $b) {
    if ($b == 0) {
        throw new Exception("Cannot divide by zero!");
    }
    return $a / $b;
}

try {
    echo divide(10, 0);
} catch (Exception $e) {
    echo "Error: " . $e->getMessage();
}
?>

🔥 What’s happening?
✅ If $b == 0, it throws an exception.
✅ The catch block handles the error instead of crashing the script.

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4️⃣ Logging Errors Instead of Displaying Them

On a live site, we shouldn’t show errors to users. Instead, log them to a file.

Step 1: Create a Log File

touch error_log.txt
chmod 666 error_log.txt

Step 2: Configure PHP to Log Errors

error_reporting(E_ALL);
ini_set("log_errors", 1);
ini_set("error_log", "error_log.txt");

🔥 Now errors are logged to error_log.txt instead of being displayed! 🎯

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5️⃣ Custom Error Handling in PHP

💡 Instead of using PHP’s default error messages, let’s create a custom error handler.

Example: Custom Error Handler

<?php
function customErrorHandler($errno, $errstr, $errfile, $errline) {
    $error_message = "[ERROR $errno] $errstr in $errfile on line $errline\n";
    error_log($error_message, 3, "error_log.txt"); // Log errors to file
    echo "Oops! Something went wrong. Please try again later.";
}

// Set custom error handler
set_error_handler("customErrorHandler");

// Trigger an error
echo $undefined_var; // Undefined variable
?>

🔥 What’s happening?
✅ Logs errors to error_log.txt.
✅ Displays a friendly error message instead of PHP’s ugly errors.

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6️⃣ Using set_exception_handler() for Uncaught Exceptions

💡 By default, uncaught exceptions stop execution. Let’s handle them better.

Example: Global Exception Handler

<?php
function globalExceptionHandler($exception) {
    $error_message = "[EXCEPTION] " . $exception->getMessage() . "\n";
    error_log($error_message, 3, "error_log.txt"); // Log exception
    echo "Oops! Something went wrong.";
}

// Set exception handler
set_exception_handler("globalExceptionHandler");

// Trigger an exception
throw new Exception("This is a test exception!");
?>

🔥 What’s happening?
✅ Handles uncaught exceptions globally.
✅ Logs them instead of crashing the site.

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7️⃣ Creating a Complete Error Handling System

🚀 Let’s build a fully functional error-handling system with:
✅ Logging to a file
✅ Custom error messages
✅ Handling fatal errors

1️⃣ Create error_handler.php

<?php
class ErrorHandler {
    public static function handleErrors($errno, $errstr, $errfile, $errline) {
        $error_message = "[ERROR] $errstr in $errfile on line $errline\n";
        error_log($error_message, 3, "error_log.txt");
        echo "An error occurred. Please try again later.";
    }

    public static function handleExceptions($exception) {
        $error_message = "[EXCEPTION] " . $exception->getMessage() . "\n";
        error_log($error_message, 3, "error_log.txt");
        echo "An unexpected error occurred. Please try again.";
    }

    public static function handleShutdown() {
        $error = error_get_last();
        if ($error !== null) {
            $error_message = "[FATAL ERROR] {$error['message']} in {$error['file']} on line {$error['line']}\n";
            error_log($error_message, 3, "error_log.txt");
        }
    }
}

// Register error handlers
set_error_handler(["ErrorHandler", "handleErrors"]);
set_exception_handler(["ErrorHandler", "handleExceptions"]);
register_shutdown_function(["ErrorHandler", "handleShutdown"]);
?>

2️⃣ Test Error Handling in index.php

<?php
require "error_handler.php";

// Trigger a notice
echo $undefined_var;

// Trigger an exception
throw new Exception("Something went wrong!");

// Trigger a fatal error
non_existent_function();
?>

🔥 What happens?
✅ Logs all errors, exceptions, and fatal errors.
✅ Displays friendly error messages to users.

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🚀 Final Thoughts

Now you can handle errors like a pro!
✅ Use try...catch for exceptions
✅ Log errors instead of displaying them
✅ Create custom error handlers
✅ Handle fatal errors gracefully

👉 Next: Session Management in PHP

Happy coding! 🎉🚀