With the last version of PHP, there are many actual methods included in the core language that you should use in your code files. These will help you a lot that you might have working out the easist way to creat a salt. So, if you are able to do, I suggest you to switch to using this method everywhere (if possible) you generate passwords.

Hashing Logic is as simple as you doing this:

password_hash('YouRSuperSecure&(*$p880$0w0rd!', PASSWORD_BCRYPT);

Example:- 

password_hash('YouRSuperSecure&(*$p880$0w0rd!', PASSWORD_BCRYPT, ['cost' => 16]);

Access to plugin and theme code is available in the WordPress dashboard. You can do one thing to protect the site from trifile to disable the both of these editors. Open your wp-config.php file and add the following constant:

define('DISALLOW_FILE_EDIT',true);

Now, when you are in the dashboard it is impossible to access the theme or plugin editor, even if you are admin.

you can try this to redirect your own url when clicking browser back button

<script>

jQuery(document).ready(function($) {

      if (window.history && window.history.pushState) {

        $(window).on('popstate', function() {
          var hashLocation = location.hash;
          var hashSplit = hashLocation.split("#!/");
          var hashName = hashSplit[1];

          if (hashName !== '') {
            var hash = window.location.hash;
            if (hash === '') {
              alert('Back button was pressed.');
                window.location='www.yourweburlhere.com';
                return false;
            }
          }
        });

        window.history.pushState('forward', null, './#forward');
      }

    });

</script>

You need to test for the negation of the Regular Expressions because you want the validation to alert upon failure,

(is_valid = !/^[0-9]+$/.test(x))

Example :-

<form action="" method="POST" name="cdp_form" id="cdp_form">
<input type="text" id="phone_number" name="phone_number" placeholder="Enter your phone number" maxlength="10" onkeyup="validateForm()">
<button type="submit" name="SEND" class="btn btn-brown">Send</button>
</form>
<?php echo $successmsg; ?>
<script>
//form validation
function validateForm()
{
var x=document.forms["cdp_form"]["phone_number"].value
if (x==null || x=="")
  {
  alert("Phone number  field must be filled in");
  cdp_form.phone_number.focus();
  return false;
  }
else if (is_valid = !/^[0-9]+$/.test(x))
    {
    alert("Phone number field must have numeric characters");
    cdp_form.phone_number.focus();
    return false;
  }
}
</script>