How Can I Write Secure MySQL Queries Using the mysql_* Functions?

Reference: Writing Secure MySQL Code Without PDO

Introduction

MySQL queries are often plagued with security vulnerabilities and errors due to improper handling. To address this, it's crucial to understand the best practices for writing secure and reliable code.

Security Concerns with MySQL_* Functions

When using the mysql_* family of functions, common security issues arise:

• SQL Injection: Attackers can manipulate queries by injecting malicious SQL statements into user input.
• Cross-Site Scripting (XSS): Malicious JavaScript can be executed by injecting it into outputted values.

Example Usage

The following PHP code sample demonstrates how to perform a safe and secure UPDATE query using mysql_* functions:

<?php # Connect and disable mysql error output
$connection = @mysql_connect($config['host'], $config['user'], $config['pass']);

# Select database
mysql_select_db($config['db'], $connection);

# Set character set
mysql_set_charset('utf8', $connection);

# Escape user input
$id = mysql_real_escape_string($_POST['id']);
$name = mysql_real_escape_string($_POST['name']);

# Execute query
$result = mysql_query('UPDATE tablename SET name = "' . $name . '" WHERE id = "' . $id . '"', $connection);

# Handle result
if ($result) {
    echo htmlentities($name, ENT_COMPAT, 'utf-8') . ' updated.';
} else {
    trigger_error('Unable to update db: ' . mysql_error(), E_USER_ERROR);
}

?>

Key Features

• Escapes user input to prevent SQL injection.
• Encodes outputted values to mitigate XSS risks.
• Sets character encoding to handle Unicode data.
• Uses error handling to notify the user of any issues in production mode.
• Keeps the code simple and readable for easy understanding.

Conclusion

By following the best practices outlined above, you can write secure and efficient MySQL queries using the mysql_* functions. Remember, it's crucial to protect your applications from security vulnerabilities and ensure data integrity.

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