header函数打开页面的源代码

I want to redirect the page when entered password is correct thats why i am using header function but that function copy the source code of the linked php page. uPass is the name of my password field and password is the column name fetched from from the database..

    if( $_POST['uPass']==$row['password'])
    {
       echo "Entered Id and Password is valid";
       header("Location:adminForm.php");
    }

Sir in this code header function it opens source code in a alert box. Please sir help me to solve this problem.

thank you.