I just forget this function when my friend ask me about strangeness in his data he store in mysql.
He has address data in <textarea></textarea>, new line not converted to br as he thing. He just see all the input just store in single line.
After search for a while I remember this gold function :
nl2br () , new line to br
just make temporary variable before as :
now $address will contain <br> tag in mysql database.
This post for remind me in future