Questions about UBB transcoding

Now do a PHP ubb transcoding. It is useful to use the code highlighting plugin, which is

If I use NL2BR, every line will add
, there are also in the pre, causing
be called out.
If not added, then multiple lines of text will be displayed to one line. The user experience is affected if the user is asked to consider adding [BR] or empty two lines to represent a br.
So ask, how to add BR in the place plus BR, such as ordinary multi-line text, should not add the place is not added, such as

/

/
such as  
 

Reply to discussion (solution)
 You didn't explain the problems you were having. 
The pre tag will take the carriage return newline as the true carriage return line character, that is, if there is a carriage return line in the string, the real result is really yellow line
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