\ban ASCII word boundary
mysqlthe literal text mysql (case sensitive) \ban ASCII word boundary
.*any character (except for line terminators), repeated any number of times
Non-Capturing Group(?:\n.*){3} {3}repeats the group contents below exactly 3 times:
\na line-feed (newline) character (ASCII 10)
.*any character (except for line terminators), repeated any number of times
\na line-feed (newline) character (ASCII 10)
.*any character (except for line terminators), repeated any number of times
\Kresets the starting point of the reported match. Any previously consumed characters are no longer included in the final match
\ban ASCII word boundary
DB_DATABASEthe literal text DB_DATABASE (case sensitive) \ban ASCII word boundary
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string