How can using backticks instead of single quotes in SQL queries impact the execution of the query in PHP?

Using backticks instead of single quotes in SQL queries can impact the execution of the query in PHP because backticks are used to escape table and column names in SQL queries, while single quotes are used to wrap string values. If backticks are used incorrectly in place of single quotes, it can lead to syntax errors in the SQL query and cause it to fail. To solve this issue, make sure to use single quotes for string values in the SQL query and backticks only for table and column names.

$query = "SELECT * FROM `users` WHERE `username` = '$username'";