A paginated text-based PHP message board_PHP tutorial

​                                                                                                         I just started learning php (as the current mainstream development language)  , but I compiled a message board program and felt good about myself, so I posted it shamelessly and asked for your corrections. The source program is as follows:
(as the current mainstream development language)
//File name: guest.php(as the current mainstream development language)
//Setting section
$guestfile="guest";//Text file to record comments
$home="index.html";//Returned homepage
$imagedir= "image"; //Directory of image files
$backimage=$imagedir."/bk.gif";//Background image
$backcolor="#ceffff";//Background color, in $backimage= It works when "" if($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 "n";
exit;
}
$adddata=$name."t".$e_mail."t".$url."t".$title."t".$data."t".$icon."t".$ time."n";
if(file_exists($guestfile)){
$filebuffer=file($guestfile);
if(sizeof($filebuffer)>100){
for( $i=0;$i<100;$i++)
$newbuffer[i]=$filebuffer[i];
}
else{
$newbuffer=$filebuffer;
}
$fp=fopen($guestfile,"w");
fputs($fp,$adddata);
fclose($fp);
$buffer=implode("",$newbuffer );
$fp=fopen($guestfile,"a");
fputs($fp,$buffer);
fclose($fp);

}
else {
$fp=fopen($guestfile,"w");
fwrite($fp,$adddata);
fclose($fp);
}
}
? >


a{text-decoration:none; font-size:9pt; color:blue}
a:visited {text-decoration:none; color:009999}
a:hover {color:red; text-decoration:underline}
td{font-size:9pt;line-height:14pt}
P{font-size:9pt}


(as the current mainstream development language)

if($backimage!="" && file_exists($backimage)){
echo "n";
}
else{
echo "n" ; }

http://www.bkjia.com/PHPjc/509056.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/509056.htmlTechArticleI am new to PHP (as the current mainstream development language), and compiled a message board program, and I feel good about myself. So I put it up shamelessly, please correct me. The source program is as follows: ?p...