Question

关于mysql_query()的问题

$sql=mysql_query("select * from admin where name='".$this->name."' and pwd='".$this->pwd."'");
$row=mysql_num_rows($sql);
echo "$row Rows\n";
关于这个语句，数据库已经连接好了，admin是其中的一个表，我已经在这个表中插入了值，name为admin，pwd为admin。但在我在登陆界面输入admin和admin并提交之后，网页显示的是0 Rows，这是怎么回事？
这是login.php里的全部代码：

<?php
mysql_connect("localhost","root","1991421");
mysql_select_db("library");
mysql_query("set names utf8");

session_start();
$A_name=$_POST[name];
$A_pwd=$_POST[pwd];

class check_input{
var $name;
var $pwd;

function check_input($a,$b){
$this->name=$a;
$this->pwd=$b;
}

function checkadmin(){
$sql=mysql_query("select * from admin where name='$this->name' and pwd='$this->pwd'");
$row=mysql_num_rows($sql);
echo "$row Rows\n";
echo "$this->name\n";
echo "$this->pwd\n";
if($row==0){
echo "<script language='javascript'>alert('用户名或密码错误！');history.back();</script>";
exit;
}
else{
echo "<script>alert('登录成功!');window.location='control_panel.php';</script>";
$_SESSION[admin_name]=$name1;
$_SESSION[pwd]=$pwd1;
}
}
}
$obj=new check_input(trim($name),trim($pwd));
$obj->checkadmin();
?>

Answer 1

$sql=mysql_query("select * from admin where name='$this->name' and pwd='$this->pwd'");
单引号内的变量~php可能不会去解析。。会被当做为一个字符串。。不防加个字符串链接吧。。
$sql=mysql_query("select * from admin where name='".$this->name."' and pwd='".$this->pwd."'");

Answer 2

改为：
$sql=mysql_query("select * from admin where name='".$this->name' ." and pwd='".$this->pwd."' ");