PHP error types and levels - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Parse Error in PHP?

A Parse Error happens when PHP finds a syntax mistake in your code, like a missing semicolon or bracket. It stops the script from running.

beginner

What does a Fatal Error mean in PHP?

A Fatal Error occurs when PHP encounters a serious problem, like calling a function that doesn't exist. It stops the script immediately.

beginner

Explain a Warning in PHP.

A Warning is a non-fatal error. PHP shows a message but continues running the script. For example, including a missing file triggers a warning.

beginner

What is a Notice in PHP?

A Notice is a minor message about something that might be a problem, like using an undefined variable. It doesn't stop the script.

intermediate

Name some common PHP error levels.

Common PHP error levels include: E_ERROR (fatal errors), E_WARNING (warnings), E_PARSE (parse errors), E_NOTICE (notices), and E_DEPRECATED (deprecated features).

Which PHP error stops the script immediately due to a serious problem?

A Warning

B Fatal Error

C Notice

D Parse Error

Fatal Errors stop the script immediately when a serious problem occurs.

What type of PHP error is caused by a syntax mistake?

A Deprecated

B Warning

C Notice

D Parse Error

Parse Errors happen when PHP finds syntax mistakes in the code.

Which PHP error level shows a message but allows the script to continue?

A Fatal Error

B Parse Error

C Warning

D Error Exception

Warnings show messages but do not stop the script.

What does a PHP Notice usually indicate?

A A minor issue like an undefined variable

B A deprecated feature

C A syntax error

D A serious error stopping the script

Notices indicate minor issues such as using undefined variables.

Which error level warns about features that will be removed in the future?

A E_DEPRECATED

B E_NOTICE

C E_WARNING

D E_PARSE

E_DEPRECATED warns about features that are outdated and will be removed.

Describe the main PHP error types and how they affect script execution.

Think about which errors stop the script and which allow it to continue.

List and explain at least three PHP error levels and give an example of when each might occur.

Consider errors that stop the script, warnings, and minor notices.

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