Are there specific guidelines for structuring and formatting SQL queries in PHP to avoid errors like missing quotation marks?

When constructing SQL queries in PHP, it's crucial to ensure that all string values are enclosed in quotation marks to avoid syntax errors. One common mistake is forgetting to include quotation marks around string values, which can lead to SQL query errors. To prevent this issue, always remember to properly format your SQL queries by enclosing string values in single or double quotation marks.

// Example of a SQL query with proper string value formatting
$query = "SELECT * FROM users WHERE username = 'john_doe'";
$result = mysqli_query($connection, $query);