10 Common PHP Errors & How to Fix Them – A Complete Beginner-Friendly Guide

PHP is one of the most widely used server-side scripting languages, but beginners and even experienced developers regularly encounter common PHP errors that break scripts or produce unexpected results.

This guide explains the 10 most frequent PHP errors, why they occur, and how to fix them with simple code examples.

You can test every example instantly using the PHP Online Compiler.

Understanding PHP Errors: Why They Occur and How to Debug

Most PHP errors fall into three categories:

• Parse Errors (Syntax Errors) – Your code has invalid syntax.
• Fatal Errors – PHP stops executing because of a serious issue.
• Warnings & Notices – Non-fatal issues but can affect output.

By learning to fix these errors quickly, you will improve your productivity, debugging skills, and code quality.

1. PHP Parse Error: Syntax Error – Unexpected Token

High-Ranking Longtail Keyword:

“PHP syntax error unexpected end of file fix”

A syntax error means PHP cannot interpret your code due to incorrect structure.

Common causes:

• Missing semicolon ;
• Missing parentheses, braces, or quotes
• Wrong syntax or typos

Example Error:

Parse error: syntax error, unexpected '}' in file.php on line 12

Fix:
Check for missing or extra symbols.

Correct Example:

<?php
echo "Hello World";
?>

2. Undefined Variable Notice

Occurs when you use a variable that has not been declared.

Error Example:

Notice: Undefined variable: name

Fix:
Always define variables before using them.

<?php
$name = "John";
echo $name;
?>

You can experiment live using the PHP Online Compiler.

3. Undefined Index Error in PHP Arrays

Longtail Keyword:

“How to fix PHP undefined index error in associative arrays”

This happens when you try to access an array key that doesn’t exist.

echo $_POST['username'];

If username is missing → Undefined index error

Fix:
Check before accessing:

if (isset($_POST['username'])) {
    echo $_POST['username'];
}

4. Call to Undefined Function

This occurs when you call a function that PHP cannot find.

Causes:

• Function spelled incorrectly
• Missing include or require file
• Using unavailable built-in functions

Fix Example:

include "functions.php";
sayHello();   // Works if included

5. Fatal Error: Maximum Execution Time Exceeded

Longtail Keyword:

“PHP maximum execution time exceeded infinite loop fix”

Happens when a script takes too long, usually due to infinite loops or heavy operations.

Fix:
Repair the loop or increase the time:

ini_set('max_execution_time', 60);

Better solution → Fix your logic, not the timer.

6. Warning: Division by Zero

Self-explanatory — dividing by zero is not allowed.

Fix:

if ($b != 0) {
    echo $a / $b;
}

7. Header Already Sent Error

Longtail Keyword:

“Fix PHP header already sent output buffering error”

Occurs when you try to send a header after HTML output has started.

Error Example:

Warning: Cannot modify header information - headers already sent

Fix:
Move header() before any output.

❌ Wrong:

echo "Hello";
header("Location: home.php");

✅ Correct:

header("Location: home.php");
exit;

8. PHP Memory Limit Exceeded

Happens when your script uses more memory than allowed.

Fix:
Optimize code or increase memory:

ini_set("memory_limit", "256M");

9. Missing Required File (include/require) Errors

Common errors:

• Warning: include() failed
• Fatal error: require() failed

Fix:
Check file path and file existence:

if (file_exists("config.php")) {
    require "config.php";
}

10. Accessing Object Property on Non-Object

Occurs when you access properties on something that is not an object.

$user->name;

If $user is null → Error.

Fix:

if (isset($user) && is_object($user)) {
    echo $user->name;
}

Bonus: How to Debug PHP Errors Faster

Use these techniques:

Enable Error Reporting

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

Use var_dump() to Inspect Variables

var_dump($data);

Use Online Tools

Run code instantly using:
👉 PHP Online Compiler

Useful tools to support this page:

• PHP Online Compiler – Run PHP code instantly
• PHP Cheat Sheet – Quick PHP syntax reference
• JavaScript Compiler – For frontend debugging
• JSON Formatter – Useful for APIs

FAQs – 10 Common PHP Errors & Fixes

Q1. What is the most common PHP error for beginners?
Syntax errors such as missing semicolons or braces are the most common.

Q2. How do I enable error reporting in PHP?
Use:

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

Q3. Why do I get “undefined index” in PHP?
Because you’re accessing an array key that does not exist.

Q4. How do I fix PHP fatal errors?
Read the error message carefully — it usually points to missing functions, classes, or files.

Q5. Why does PHP show “headers already sent”?
It happens when output (echo/HTML) appears before header() functions.

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Conclusion

Understanding the 10 most common PHP errors helps you debug faster, write cleaner code, and avoid mistakes that break applications. Whether you’re a student or developer, fixing these issues quickly will make you more confident in PHP development.

Start testing and fixing PHP code now using 👉 PHPOnline.in – Free PHP Compiler