What does a colon before a literal in an SQL statement mean?

Question

What does it mean to use \":\" before a variable ?

For example, :userId in this code:

public function removeUser($userI         


        

Answer 1

The colon is a common character that indicates a placeholder for a variable value in a SQL statement. In this case, the those placeholders are getting replaced by the value of userId and project_id at runtime. This is great for avoiding SQL injection vulnerabilities.