pdo - How to differentiate between php constant and string

Question

I am storing db credentials in a file as constant and including in another file. I am using PDO to connecting with database. But It's unable to differentiating between string and constant variables. So how to differentiate it to connect with database? This is my code line-

$db = new PDO("mysql:hostname='DB_HOST'; dbname='P_DB'", "'DB_USER'", "'DB_PASSKEY'");

question from:https://stackoverflow.com/questions/65879687/how-to-differentiate-between-php-constant-and-string

Answer 1

PHP constants cannot be instantiated within a string; you need to concatenate them to the string, or, in the case of your user and password fields, just reference the constant:

$db = new PDO("mysql:hostname=" . DB_HOST . ";dbname=" . P_DB, DB_USER, DB_PASSKEY);