为什么不能连接到数据库，请大家帮忙，谢谢

Question

<?php
//if (($userid!=="")and($password!=="")and($userip!=="")and($email!==""))
{
$con=mysql_connect("localhost","lj","lj");
mysql_select_db("software");
$query="insert into userinfo(userid,password,userip,email,id) values ('bbb','bbb','$bbb','bbb',null)";
$result=mysql_query("$query",$con);
setcookie("userid",$userid);
require("showsoftware.php");
exit();
}
else
{
echo "<center>您的输入不完整，请重新输入。</center>";
echo "<center><a href=showsoftware.php>返回</a></center>";
}
?>这样还是不行，不知道怎么回事了

Answer 1

$con=mysql_connect("localhost","lj","lj");
echo mysql_error();
mysql_select_db("software");
echo mysql_error();看有没有错误信息输出.

Answer 2

改成这样：
<?php
if (($userid!=="")&($password!=="")&($userip!=="")&($email!==""))
{
$con=mysql_connect("localhost","lj","lj")or die(mysql_error());
mysql_select_db("software")or die(mysql_error());
$query="insert into userinfo(userid,password,userip,email,id) values ('$userid','$password','$userip','$email',null)";
$result=mysql_query("$query",$con)or die(mysql_error());
setcookie("userid",$userid);
require("showsoftware.php");
exit();
}
else
{
echo "<center>您的输入不完整，请重新输入。</center>";
echo "<center><a href=showsoftware.php>返回</a></center>";
}
?>
if (($userid!=="")&($password!=="")&($userip!=="")&($email!==""))
还可以改成：if(!empty($userid)&!empty($passsword)&!empty($userip)&!empty($email))或者if(isset($userid)&isset($password)&isset($userip)&isset($email))