登记验证一直失败

     require_once 'db.php'; 
     session_start();
     
     $name =  $_POST["name"] ;
     $mail = $_POST["email"] ;
	 $pwd=  $_POST["key"] ;
	 $pwd2 =  $_POST["rekey"] ;
	 $agreement =  $_POST["agreement"] ;
     
	 
	 if($agreement=="T"){
	 	if($pwd==$pwd2){
	 		$sql="select * from user";
		    $result = $db->query($sql);		 
		    if($result && $row=$result->fetch_assoc()){
		    	if($name==$row["name"]){
			 	 	echo '";
					exit;
			    }elseif($mail==$row["mail"]){
			 	 	echo '";
					exit;
			 	}else{
			 		$sql="insert into user(name,represent,pwd,mail,time) value('{$name}',0,'{$pwd}','{$mail}',now())";
					$result = $db->query($sql);
					if($result && $db->affected_rows>0){
						$sql="select * from user where name='{$name}'";
						$result = $db->query($sql);
						if($result && $row=$result->fetch_assoc()){
							$uid=$row['uid'];
						}
					}			
					$result->free_result;
		            $db->close;	
					
					$sql="insert into userphoto(uid,name,type,url,size,time) value('{$uid}','steve','.png','./img/userphoto/steve.png','6.24kb',now())";
				    $result = $db->query($sql);
		            if($result && $db->affected_rows>0){
				     	echo '";
				        exit;
				    }else{
				        echo '";
						exit;
				    }
			 	}
		    }
			$result->free_result;
            $db->close;		 	
	 	}else{
	 		echo '";
			exit;
	 	}
	 }else{
	 	echo '";
		exit;
	 }   
     $result->free_result;
     $db->close;
?>