make sure to do proper escapes on anything that needs escaping. So escape
OS/2 to OS\/2
7.0 to 7\.0
etc.
. / ? * etc etc are all special to preg, so you should not use them in your pattern unless you escape them or when you want to use their “special powers”
UPDATE: Had to put it in codeblock to see the escapes 😉
solved Php – Delimiter must not be alphanumeric or backslash [duplicate]