PHP验证mysql登录用户名和密码

<?php
function Useragreed($username,$password) {
$sql="SELECT * from `user` WHERE user_name='$username' AND user_pass='$password'";
$result=mysql_query($sql);
if(mysql_num_rows($result) == 0){

return false;
}else{

return true;
}
}

if(USeragreed(接收到的用户名,接受到的密码)){
echo'登陆成功!';
}else{
echo'登陆失败1';

}