Escape string with single quotes in PHP for SQLite

I would like to store the following string in the field of an SQLite table:

$string = "Einstein's equation";

Is there a function to do so in a safe way? Obviously

SQLite3::escapeString($string);

does not work. Instead it will return Einstein"s equation.

I read that in SQL one is supposed to use double single quotes for single quotes, i.e., Einstein''s equation. However, if I try to make it safe SQLite3::escapeString("Einstein''s equation") returns Einstein""s equation. Is that a bug of escapeString?

What would be the correct way to escape a string with single quotes properly?