25 Common PHP Errors and How to Fix Them
25 Common PHP Errors and How to Fix Them
Every PHP developer encounters errors while coding. Learning how to identify and fix these errors quickly can save hours of debugging.
This guide covers the most common PHP errors, explains why they occur, and shows how to fix them with examples.
1. Parse Error: Syntax Error
Error
Parse error: syntax error, unexpected ';'
Cause
Missing or extra characters like ;, {, }, or quotes.
Example
<?php
echo "Hello"
?>
Fix
<?php
echo "Hello";
?>
2. Undefined Variable
Error
Notice: Undefined variable
Cause
Using a variable before assigning a value.
echo $name;
Fix
$name = "Sunil";
echo $name;
3. Undefined Index
Error
Undefined array key
Cause
Accessing an array element that doesn't exist.
Fix
if(isset($_POST["email"])){
echo $_POST["email"];
}
4. Call to Undefined Function
Error
Fatal error: Call to undefined function
Cause
Misspelled function name or missing extension.
Fix
Check the spelling and ensure the required PHP extension is enabled.
5. Cannot Modify Header Information
Error
Headers already sent
Cause
Output is sent before header().
Wrong
echo "Welcome";
header("Location: home.php");
Correct
header("Location: home.php");
exit;
6. Division by Zero
Wrong
echo 100 / 0;
Fix
if($number != 0){
echo 100 / $number;
}
7. Database Connection Failed
Cause
Wrong database credentials.
Fix
Verify:
Host
Username
Password
Database Name
8. SQL Syntax Error
Always print the SQL query and verify it before execution.
9. Session Not Working
Always start sessions before any HTML output.
session_start();
10. File Upload Not Working
Check:
Form method is POST
enctype="multipart/form-data"Upload folder permissions
PHP upload limits
11. White Screen of Death
Enable error reporting.
error_reporting(E_ALL);
ini_set('display_errors',1);
12. 404 Page Not Found
Check:
File name
URL
Rewrite rules
Server configuration
13. Include File Failed
Wrong
include "config.php";
If the file is in another folder:
include "includes/config.php";
14. Undefined Function mysqli_connect()
The MySQLi extension is disabled.
Enable it in your PHP installation.
15. Maximum Execution Time Exceeded
Increase:
max_execution_time
Or optimize your code.
16. Allowed Memory Size Exhausted
Increase:
memory_limit = 256M
17. Password Verification Failed
Always use:
password_hash()
and
password_verify()
18. JSON Decode Returns Null
Always check:
json_last_error_msg();
19. Timezone Warning
Set the timezone.
date_default_timezone_set("Asia/Kolkata");
20. Invalid Argument for foreach()
Wrong
foreach($users as $user)
When $users isn't an array.
Fix
if(is_array($users)){
foreach($users as $user){
}
}
21. Missing Semicolon
One of the most common beginner mistakes.
Always end PHP statements with:
;
22. Wrong File Permissions
If PHP cannot write files:
Linux example:
chmod 755 uploads
23. Email Not Sending
Check:
SMTP configuration
Mail server
Firewall
Use PHPMailer instead of the native
mail()function.
24. Invalid JSON Response
When building APIs:
header("Content-Type: application/json");
Return valid JSON.
25. Blank Page After Deployment
Check:
PHP version
File permissions
Error logs
Missing extensions
Database credentials
Debugging Tips Every PHP Developer Should Know
Enable error reporting during development.
Read the complete error message before changing code.
Use
var_dump()andprint_r()to inspect variables.Log errors to a file instead of displaying them in production.
Test your application in a local environment before deployment.
Keep PHP and dependencies updated.
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