Parse error: parse error, expecting `','' or `';'' in D:\..... on line 9 请大神帮忙，在线等

Question

<?php
$cid=$_GET["cid"];
$mysqli=new mysqli("localhost","root","wangluo12345","book");
$result=$mysqli->query("select id, bookname from book where cid={$cid}");
while($row=$result->fetch_assoc()){
echo '<ul>';
echo '<li><a href="con.php?id='_$row["id"]_'">'_$row["bookname"]_'</a></li>';
echo '</ul>';
}
?>

Answer 1

echo '<li><a href="con.php?id='.$row["id"].'">'.$row["bookname"].'</a></li>';

字符串连接 不能用 _ 得用 .