PHP error types and levels - Mini Project: Build & Apply

Understanding PHP Error Types and Levels

📖 Scenario: You are building a simple PHP script to learn about different types of errors and how PHP reports them. This will help you understand how to spot and fix problems in your PHP code.

🎯 Goal: Create a PHP script that defines error reporting levels, triggers different types of errors, and displays the error messages.

📋 What You'll Learn

Create variables and settings to control error reporting

Trigger different PHP error types: notice, warning, and fatal error

Display error messages according to the error reporting level

💡 Why This Matters

🌍 Real World

Understanding PHP error types helps you debug your web applications and fix problems quickly.

💼 Career

PHP developers must know how to handle errors to write reliable and maintainable code.

1

Set up error reporting levels

Write PHP code to set the error reporting level to show all errors using error_reporting(E_ALL); and enable displaying errors with ini_set('display_errors', '1');.

PHP

<?php
// Set error reporting to show all errors
// Your code here

Hint

Use error_reporting(E_ALL); to report all errors and ini_set('display_errors', '1'); to show them on the screen.

2

Trigger a notice error

Add PHP code that tries to use an undefined variable called $undefinedVar to trigger a notice error.

PHP

<?php
error_reporting(E_ALL);
ini_set('display_errors', '1');
// Use the variable $undefinedVar to trigger a notice error
// Your code here

Hint

Simply try to print $undefinedVar without defining it first.

3

Trigger a warning error

Add PHP code to include a file named missingfile.php using include to trigger a warning error.

PHP

<?php
error_reporting(E_ALL);
ini_set('display_errors', '1');
echo $undefinedVar;
// Include a missing file to trigger a warning error
// Your code here

Hint

Use include 'missingfile.php'; to cause a warning because the file does not exist.

4

Trigger a fatal error

Add PHP code to call a function named undefinedFunction() that does not exist to trigger a fatal error. Then print "End of script" using echo.

PHP

<?php
error_reporting(E_ALL);
ini_set('display_errors', '1');
echo $undefinedVar;
include 'missingfile.php';
// Call undefinedFunction() to trigger a fatal error
// Then print "End of script"
// Your code here

Hint

Call undefinedFunction(); to cause a fatal error. The last echo will not run because of the fatal error.

Practice

1. Which PHP error type indicates a problem that stops the script from running?

easy

A. Warning

B. Fatal error

C. Notice

D. Deprecated

Solution

1. Step 1: Understand PHP error types

   Fatal errors are serious problems that stop the script immediately.

2. Step 2: Compare with other error types

   Warnings and notices do not stop the script; deprecated warns about old code.

3. Final Answer:

   Fatal error -> Option B

4. Quick Check:

   Fatal error = stops script [OK]

Hint: Fatal errors stop scripts immediately, others do not [OK]

Common Mistakes:

• Confusing warnings with fatal errors
• Thinking notices stop script execution
• Mixing deprecated warnings with fatal errors

2. Which of the following is the correct way to set PHP to report all errors except notices?

easy

A. error_reporting(E_ALL & ~E_NOTICE);

B. error_reporting(E_ALL | E_NOTICE);

C. error_reporting(E_ALL & E_NOTICE);

D. error_reporting(E_ALL ^ E_NOTICE);

Solution

1. Step 1: Understand error_reporting flags

   E_ALL means all errors; ~E_NOTICE means exclude notices using bitwise NOT.

2. Step 2: Analyze each option

   error_reporting(E_ALL & ~E_NOTICE); uses bitwise AND with NOT (~) to exclude notices correctly.

3. Final Answer:

   error_reporting(E_ALL & ~E_NOTICE); -> Option A

4. Quick Check:

   Exclude notices with & ~E_NOTICE [OK]

Hint: Use & ~E_NOTICE to exclude notices from all errors [OK]

Common Mistakes:

• Using | instead of & ~ to exclude errors
• Confusing ^ (XOR) with exclusion
• Using & E_NOTICE which includes only notices

3. What will be the output of this PHP code?

<?php
error_reporting(E_ERROR | E_WARNING);
echo $undefined_variable;
include('missing_file.php');
?>

medium

A. Warning about missing file only

B. Fatal error about missing file

C. Notice about undefined variable and warning about missing file

D. No output, script runs silently

Solution

1. Step 1: Check error_reporting level

   Only E_ERROR and E_WARNING are reported; notices are not shown.

2. Step 2: Analyze code behavior

   Undefined variable triggers a notice (not shown). Missing file triggers a warning (shown).

3. Final Answer:

   Warning about missing file only -> Option A

4. Quick Check:

   E_WARNING shown, notices hidden [OK]

Hint: Only errors and warnings show; notices are hidden [OK]

Common Mistakes:

• Expecting notice output when it's excluded
• Confusing warning with fatal error
• Thinking script stops on warning

4. Identify the error in this PHP code snippet:

<?php
error_reporting(E_ALL);
ini_set('display_errors', 0);
echo $undefined_var;
?>

medium

A. Errors will be displayed despite display_errors set to 0

B. No errors will be reported because error_reporting is off

C. Syntax error due to missing semicolon

D. Errors are reported but not displayed due to display_errors=0

Solution

1. Step 1: Understand error_reporting and display_errors

   error_reporting(E_ALL) enables all error reporting; display_errors=0 hides errors from output.

2. Step 2: Analyze code behavior

   Errors are logged/reported internally but not shown on screen because display_errors is off.

3. Final Answer:

   Errors are reported but not displayed due to display_errors=0 -> Option D

4. Quick Check:

   display_errors=0 hides errors, reporting still active [OK]

Hint: display_errors=0 hides errors; error_reporting controls reporting [OK]

Common Mistakes:

• Thinking errors won't be reported at all
• Confusing display_errors with error_reporting
• Assuming syntax error due to missing semicolon

5. You want to show all errors except deprecated warnings during development but hide all errors on the live site. Which code setup achieves this best?

hard

A. error_reporting(E_ALL); ini_set('display_errors', 1);

B. error_reporting(E_ALL & ~E_NOTICE); ini_set('display_errors', 0);

C. if (ENV == 'dev') { error_reporting(E_ALL & ~E_DEPRECATED); ini_set('display_errors', 1); } else { error_reporting(0); ini_set('display_errors', 0); }

D. if (ENV == 'prod') { error_reporting(E_ALL); ini_set('display_errors', 1); } else { error_reporting(0); ini_set('display_errors', 0); }

Solution

1. Step 1: Understand environment-based error settings

   During development (dev), show all errors except deprecated; on live (prod), hide all errors.

2. Step 2: Analyze each option

   if (ENV == 'dev') { error_reporting(E_ALL & ~E_DEPRECATED); ini_set('display_errors', 1); } else { error_reporting(0); ini_set('display_errors', 0); } correctly uses error_reporting with exclusion and display_errors on dev, off on live.

3. Final Answer:

   if (ENV == 'dev') { error_reporting(E_ALL & ~E_DEPRECATED); ini_set('display_errors', 1); } else { error_reporting(0); ini_set('display_errors', 0); } -> Option C

4. Quick Check:

   Dev shows errors except deprecated; live hides all [OK]

Hint: Use environment check to toggle error reporting and display [OK]

Common Mistakes:

• Showing errors on live site
• Not excluding deprecated warnings during dev
• Confusing environment variable names