Common PHP Errors and How to Fix Them

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PHP errors are messages shown by the PHP engine when something goes wrong in your code. These errors tell you what the problem is and where it happened in your file. They help developers find and fix mistakes like missing semicolons, undefined variables, or wrong function names.

In simple words — a PHP error means your code has a problem that stops it from running properly or gives unexpected results.

If you are learning PHP or building your first web application, you have probably seen scary messages like:

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

Don’t worry — it happens to every developer.
PHP errors are common and usually easy to fix once you understand what they mean.

In this guide, we’ll cover the most common PHP errors, explain why they happen, and show you simple ways to fix them.
By the end, you’ll be able to debug your PHP code confidently and save hours of frustration.

1. Parse Error (Syntax Error)

What It Means

A parse error happens when PHP cannot understand your code because of a syntax mistake — like a missing semicolon, unclosed quote, or misplaced bracket.

Example

<?php
echo "Hello World"
?>

🚫 Error Message

Parse error: syntax error, unexpected end of file in index.php on line 2

✅ How to Fix

You forgot a semicolon (;) at the end of the statement. Fix it like this:

<?php
echo "Hello World";
?>

🔍 Tip

Always check:

  • Missing semicolons (;)
  • Unmatched parentheses (), braces {}, or brackets []
  • Unclosed quotes (", ')

Using an editor like VS Code or PhpStorm can highlight these issues automatically.

2. Undefined Variable

What It Means

This error appears when you use a variable that was never declared or initialized.

Example

<?php
echo $name;
?>

🚫 Error Message

Notice: Undefined variable: name in index.php on line 2

✅ How to Fix

Always initialize your variables before using them.

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

🔍 Tip

You can use the isset() or empty() function to check if a variable exists before using it:

if (isset($name)) {
  echo $name;
}

3. Undefined Index

What It Means

You’re trying to access an array element or a form field that doesn’t exist.

Example

<?php
echo $_POST['email'];
?>

If the form doesn’t contain an input named “email,” PHP will show an undefined index warning.

🚫 Error Message

Notice: Undefined index: email in form.php on line 2

✅ How to Fix

Use isset() to check whether the index exists:

if (isset($_POST['email'])) {
    echo $_POST['email'];
} else {
    echo "Email not provided";
}

4. Undefined Function

What It Means

This error means you’re calling a function that doesn’t exist or has a typo.

Example

<?php
ech("Hello");
?>

🚫 Error Message

Fatal error: Uncaught Error: Call to undefined function ech() in index.php on line 2

✅ How to Fix

Check for typos or ensure the function is defined before calling it.

<?php
echo("Hello");
?>

If you’re calling a custom function, make sure the file containing it is included:

include 'functions.php';
myFunction();

5. Fatal Error: Call to Undefined Method

What It Means

You’re calling a method that doesn’t exist in a class or object.

Example

class User {
    public function login() {
        echo "User logged in";
    }
}

$obj = new User();
$obj->logout();

🚫 Error Message

Fatal error: Uncaught Error: Call to undefined method User::logout()

✅ How to Fix

Check the class and make sure the method exists or that you spelled it correctly.

$obj->login();

6. Missing File or Include Error

What It Means

This error occurs when PHP can’t find the file you’re trying to include or require.

Example

<?php
include('header.php');
?>

If header.php doesn’t exist or the path is wrong:

🚫 Error Message

Warning: include(header.php): failed to open stream: No such file or directory

✅ How to Fix

Check your file path:

  • Is the file name correct (case-sensitive)?
  • Is the path relative to the current file?

Example:

include 'includes/header.php';

If the file is essential for running the app, use require instead of include.

7. Division by Zero

What It Means

PHP cannot divide a number by zero — it’s mathematically invalid.

Example

<?php
$num = 10;
$div = 0;
echo $num / $div;
?>

🚫 Error Message

Warning: Division by zero in math.php on line 3

✅ How to Fix

Check the denominator before dividing:

if ($div != 0) {
    echo $num / $div;
} else {
    echo "Cannot divide by zero!";
}

8. Headers Already Sent

What It Means

You’re trying to send HTTP headers (like header() or setcookie()) after PHP has already sent output to the browser.

Example

<?php
echo "Welcome!";
header("Location: home.php");
?>

🚫 Error Message

Warning: Cannot modify header information - headers already sent by (output started at index.php:2)

✅ How to Fix

Always call header() or setcookie() before any HTML or echo output:

<?php
header("Location: home.php");
exit;
?>

Or use output buffering:

<?php
ob_start();
echo "Hello";
header("Location: home.php");
ob_end_flush();
?>

9. Maximum Execution Time Exceeded

What It Means

Your PHP script took too long to run. This usually happens with infinite loops or large data operations.

Example

<?php
while (true) {
    echo "Running...";
}
?>

🚫 Error Message

Fatal error: Maximum execution time of 30 seconds exceeded in script.php

✅ How to Fix

  1. Fix the logic to avoid infinite loops.
  2. Increase the execution time (only if needed):
ini_set('max_execution_time', 60); // 60 seconds

10. Memory Limit Exhausted

What It Means

Your script used more memory than PHP allows (default 128MB or 256MB).

Example

<?php
$bigArray = range(1, 100000000);
?>

🚫 Error Message

Fatal error: Allowed memory size of 134217728 bytes exhausted

✅ How to Fix

  1. Optimize your code (avoid loading huge arrays).
  2. Increase the limit temporarily:
ini_set('memory_limit', '512M');

11. Object Not Found / Null Object

What It Means

You’re trying to access an object property or method on a variable that is null or not an object.

Example

<?php
$user = null;
echo $user->name;
?>

🚫 Error Message

Fatal error: Uncaught Error: Attempt to read property "name" on null

✅ How to Fix

Check if the object is valid before accessing it:

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

Or use PHP 8’s null-safe operator:

echo $user?->name;

12. SQL Injection or Query Errors

What It Means

Your SQL query failed, often because of missing quotes, wrong syntax, or unsafe user input.

Example

<?php
mysqli_query($conn, "SELECT * FROM users WHERE id = $id");
?>

If $id contains text, this fails.

✅ How to Fix

Always use prepared statements:

$stmt = $conn->prepare("SELECT * FROM users WHERE id = ?");
$stmt->bind_param("i", $id);
$stmt->execute();

Bonus Tips: How to Debug PHP Errors Like a Pro

  1. Turn on Error Reporting (for Development Only)
    Add this at the top of your file:
   ini_set('display_errors', 1);
   error_reporting(E_ALL);
  1. Check Your Error Log File
    In your php.ini file, find the path:
   error_log = /var/log/php_errors.log
  1. Use var_dump() and print_r()
    To inspect variables and arrays while debugging:
   var_dump($data);
  1. Use Xdebug for Advanced Debugging
    Xdebug helps you trace errors, performance, and step through code in VS Code or PhpStorm. 🏁 Conclusion

PHP errors are not your enemies — they are your best teachers.
Every warning or notice points directly to what went wrong and where to fix it.

By understanding the most common PHP errors — from syntax mistakes to undefined variables and header issues — you can easily build cleaner, more stable, and professional web applications.

Remember:

  • Always enable error reporting while developing.
  • Test your code step-by-step.
  • Use IDEs that highlight errors automatically.

Once you master debugging, you’ll find PHP development faster, easier, and far more enjoyable!

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