为什么数据库名称出现在文本输入中?

I create a php file in my database which just includes some text input. I don't have any php script in the file. So why the name of my database appears in the text inputs?

This is source code (that is all I got but the web requires to have more text +.+) :

 <!DOCTYPE html>

<html>
    <head>
        <title>Log in</title>
        <meta charset="utf-8" />
        <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <link rel='stylesheet' href='style.css' />

        <style>
            .container {
                border:1px solid grey;
                padding: 20px;
                margin: 20px auto;
                display: table;

            }

        </style>

    </head>

    <body>
    <nav>
        <ul>
            <li>Home<li>
            <li>Contact</li>
            <li>
                <form method="post" action="main.php">
                    <input type="email" name="email" placeholder="Email" /> 
                    <input type="password" name="password" placeholder="Password" /> 
                    <input type="submit" name="submit" value="Log In" />
                </form>
            </li>
        </ul>
    </nav>
    <div class = "container">
        <form method="post">
            <input type="email" name="email" placeholder="Email" /> 
            <input type="password" name="password" placeholder="Password" /> 
            <input type="text" name="firstName" placeholder="First Name" /> 
            <input type="text" name="lastName" placeholder="Last Name" /> 
            <input type="submit" name="submit" value="Sign Up" />           
        </form>
    </div>  

    </body>
</html>