Is it correct to use Singleton for db class and templating engine?

Question

PHP

Good day. I decided to "ride" a little for practice and write a class for working with the database, as well as a small template engine. Googling, I saw that some people write such classes using a singleton. As I understand it, in order to access a single instance of an object from any corner of the application. Do I need to go this way and if not, advise which design patterns to use / not use for these purposes.

Answer 1

No.
Read about DI .
Why everything else is bad:
github.com/codedokode/pasta/blob/master/arch/di.md
PHP implementations:
github.com/ziadoz/awesome-php#dependency-injection .

Answer 2

Is it correct to use Singleton for db class and templating engine?

No, not correctly
connections can be MANY, to different bases.
the template engine object, if it contains values ​​assigned by the user, can have a second instance for processing some independent pieces of code ,
and you also have a class for the database - database.phpinfo.su
ONLY 1 instance of the class. For example, a Request and Response object.

Answer 3

Can.
There is nothing wrong with having a global link to access the database.