A paging text-based PHP message board _ PHP Tutorial

A paging text-based PHP message board. The younger brother is a beginner in php (as the mainstream development language) and has compiled a message board program. he feels good about himself, so he put his face up. please correct me. The source code is as follows :? P's younger brother is new to php (as the mainstream development language). he compiled a message board program and felt good about himself, so he put his face up. please correct me. The source program is as follows:
// File name: guest. php (as the mainstream development language)
// Settings
$ Guestfile = "guest"; // record the text file of the message
$ Home = "index.html"; // return to the home page
$ Imagedir = "image"; // image file directory
$ Backimage = $ imagedir. "/bk.gif"; // background image
$ Backcolor = "# ceffff"; // background color, which takes effect when $ backimage = ""
?>


If ($ QUERY_STRING! = ""){
$ Page = $ QUERY_STRING;
} Else {
$ Page = 1;
}
If ($ mode = "add "){
$ Name = htmlspecialchars (trim ($ name ));
$ Title = htmlspecialchars (trim ($ title ));
$ Data = nl2br (htmlspecialchars ($ data ));
$ Data = str_replace ("r", "", $ data );
$ Data = str_replace ("x0A", "", $ data );
$ Data = str_replace ("", "", $ data );
If ($ data = "") $ data = "";
$ E_mail = trim ($ e_mail );
If ($ e_mail = "") $ e_mail = 0;
$ Url = trim ($ url );
If ($ url = "http: //" | $ url = "") $ url = 0;
$ Time = date ("Y "). "Year ". date ("m "). "Month ". date ("d "). "Day [". date ("H "). ":". date ("I "). ":". date ("s "). "]";
If ($ name = "" | $ title = ""){
Echo"