php-the newly learned PHP, but still do not connect the database, there is a small problem

PHP Database

Ask how to build a database? Landing can already be completed, is the message function can not be achieved

 
   
    
   <title>Message boards</title>Return
   connected!
"; $selected = mysql_select_db ("center");//if ($selected)//echo "selected!
"; mysql_query (" Set names ' UTF8 ' "); $insert _account = $_session[' account ']; $insert _pwd = $_session[' password '];echo $ Insert_account;//echo $_post[comment];if ($_session[' check '] ==1) {if (!empty ($_post[comment])) {$sql = "INSERT into  Comment (account,comment,time) VALUES (' $insert _account ', ' $_post[comment] ', ' $printtime '); mysql_query ($sql) or Die (Mysql_error ()); $_session[' check '] = 0;} else echo ' Welcome to the message board ';} $insert _account?>
   
    "> Please leave a message
    <textarea name="comment" rows="5" cols="40"><?php//echo ReadFile ("Webdictionary.txt");? ></textarea>
    
    
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   !--? php Do {$i + +,?--> 
     !--? php} while ($myrow = Mysql_fetch_array ($rs)); echo ""; } echo "Shared". $pages. " Page (". $page." /". $pages.") "; for ($i =1; $i < $page; $i + +) echo "[". $i. "]"; echo "[". $page. "]"; for ($i = $page +1; $i <= $pages; $i + +) echo "[". $i. "]"; echo ""; ?>!----> 
    
 
    
 
     
 
      
 
 message 
 
 
      
 
 release time 
 
 
      
 
 Message user 
 
 
     
 
      
 
 
      
!--? php echo $myrow ["Time"]?--> 
 
      
!--? php echo $myrow ["Accou NT "]?-->