Eclipse - Content-Length header already present

I'm encountering a really weird problem while doing php development in Eclipse. I try to submit a very simple html form.

<form id="registerForm" action="login.php" method="post">
    <div class="reg-container">
        <h1 class="reg-label">Login</h1>
        <label><b>Username</b></label> <input id="username" type="text"
            placeholder="Enter Username" name="username"> 
            <label><b>Password</b></label> <input id="password"
            type="password" placeholder="Enter Password" name="password"> 
        <button type="submit" class="registerbtn" name="login">Login</button>
    </div>
    <div class="reg-container">
        <p>
            Not a member? <a href="register.php">Login</a>
        </p>
    </div>
</form>

After I click Login to submit the form. Chrome gives me this

In eclipse console there is no error message.
I have breakpoint at beginning of my login.php, but it never reaches there.
Please help. Thank you.