Fatal error of PHP [duplicate] - php

Question

This question already has answers here:
Isset expression error
(3 answers)
Closed 6 years ago.
I'm doing an admin panel and I'm doing a form for adding users. My code below:
<form class="form-horizontal">
<fieldset>
<!-- Form Name -->
<legend>Add user</legend>
<!-- Prepended text-->
<div class="form-group">
<label class="col-md-4 control-label" for="newuser">Username</label>
<div class="col-md-4">
<div class="input-group">
<span class="input-group-addon">#</span>
<input id="newuser" name="newuser" class="form-control" placeholder="Username" type="text" required="">
</div>
<p class="help-block">Put the new users username here</p>
</div>
</div>
<!-- Password input-->
<div class="form-group">
<label class="col-md-4 control-label" for="userpw">New user password</label>
<div class="col-md-4">
<input id="userpw" name="userpw" type="password" placeholder="Password" class="form-control input-md" required="">
<span class="help-block">Enter new user's password here!</span>
</div>
</div>
<!-- Select Basic -->
<div class="form-group">
<label class="col-md-4 control-label" for="permissions">Choose permissions</label>
<div class="col-md-4">
<select id="permissions" name="permissions" class="form-control">
<option value="1">System administrator</option>
<option value="2">Editor</option>
<option value="3">Developer</option>
<option value="4">Normal user</option>
</select>
</div>
</div>
<!-- Button -->
<div class="form-group">
<label class="col-md-4 control-label" for="btn_send">Send request to server</label>
<div class="col-md-4">
<button id="btn_send" name="btn_send" class="btn btn-primary">Send it!</button>
</div>
</div>
</fieldset>
</form>
<?php
$newuser = $_GET['newuser'];
$userpw = $_GET['userpw'];
$permission = $_GET['permissions'];
if(isset($newuser and $userpw and $permission) {
$sql = "INSERT INTO users(username,userpw,permission)VALUES('$newuser', '$userpw','$permission')";
mysql_query($sql);
}
else {
echo "error";}
And I Get:
Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead) in C:\xampp\htdocs\lumino\usermanagement.php on line 95
I couldn't fix it anyhow, playing with this for like 5 hours.
It's doing $_GET method, so I get the url like:
mysite.com/usermanagement.php?newuser=Berkay&userpw=18042003&permissions=3&btn_send=

Answer 1

Using isset, you can't have multiple items inside it:
if(isset($newuser and $userpw and $permission) {
Needs to become:
if(isset($newuser) && isset($userpw) && isset($permission)) {
Or:
if(isset($newuser, $userpw, $permission)) {

Answer 2

You just miss a ) and a set of ,:
if(isset($newuser, $userpw, $permission)) {
$sql = "INSERT INTO users(username,userpw,permission)VALUES('$newuser', '$userpw','$permission')";
mysql_query($sql);
}