Does WordPress function replace_hello() exists?

This is custom function the author uses to show how to use the_content filter. If you look at the line after the function add_filter('the_content', 'replace_hello');
this is saying to call the custom function replace_hello when encountering the the_content filter

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)