Php javascript conflict in wordpress template file

Question

I have built a contact form for my wordpress site. Four fields are there - name, email, subject, message. For logged in users I want their name and email to be auto-filled in their respective fields in the form and those name, email fields will be disabled for them to edit. And for non-logged in users they will put name, email fields manually. I have put this code in the page template file -

    <?php

    $current_user = wp_get_current_user();
    $user_email = $current_user->user_email;
    $user_name = $current_user->user_firstname.' '.$current_user>user_lastname;

    if ( 0 != $current_user->ID ) {

     echo '<script type="text/javascript">
     document.getElementById("curUserName").value = "'.$user_name.'";
     document.getElementById("curUserName").disabled = "disabled";
     document.getElementById("curUserEmail").value = "'.$user_email.'";
     document.getElementById("curUserEmail").disabled = "disabled";
     </script>';
     }
     ?>

But this code is disabling name, email fields for both users (logged in and non-logged in). I have controlled the script through if condition. Still the javascript is applying for both users. Please advise where I have gone wrong.

Here is the form html -

    <form action="/success.php" method="post">
<label>Name :</label><br>
<input type="text" id="curUserName" name="sender_name" required><br>
<label>Email :</label><br>
<input type="text" id="curUserEmail" name="sender_email" required><br>
<label>Subject :</label><br>
<input type="text" name="sender_sub"><br>
<label>Message</label><br>
<textarea name="sender_msg" rows="4" cols="60" required></textarea><br>
<input type="submit" name="submit" value="Send">
</form>

Answer 1

Don't echo javascript with php. It's bad practice.

Try using value tags in your inputs, check if user logged in with a ternary operator, and if so, echo to value tag their credentials .

<?php (is_user_logged_in()) ? $current_user = wp_get_current_user() : $current_user = false; ?>

<label>Name</label>
<input type="text" id="curUserName" name="sender_name" value="<?php ($current_user) ? echo $current_user->user_name : '' ?>" required>
<label>Email</label>
<input type="text" id="curUserEmail" name="sender_email" value="<?php ($current_user) ? echo $current_user->user_email : '' ?>" required>

Answer 2

The source you are going to change has disabled option already.. so just remove it if the user is not logged in :)

<?php

    $current_user = wp_get_current_user();
    $user_email = $current_user->user_email;
    $user_name = $current_user->user_firstname.' '.$current_user>user_lastname;

    echo '<script type="text/javascript">';
    if ( 0 != $current_user->ID )
    {

        echo 'document.getElementById("curUserName").value = "'.$user_name.'" 
        document.getElementById("curUserName").disabled = "disabled"
        document.getElementById("curUserEmail").value = "'.$user_email.'"
        document.getElementById("curUserEmail").disabled = "disabled"';
     }
     else
     {

        echo 'document.getElementById("curUserName").disabled = false;
        document.getElementById("curUserEmail").disabled = false;';         
     }
     echo '</script>';
 ?>