在不在Ajax的对象上下文中时使用$ this

Question

getting this error

Fatal error: Uncaught Error: Using $this when not in object context in E:\\xampp\\htdocs\\StudentGuideBook\\Version1.0\\models\\AjaxChecking.php:4 Stack trace: #0 {main} thrown in E:\\xampp\\htdocs\\StudentGuideBook\\Version1.0\\models\\AjaxChecking.php on line 4

 function checkAvailability() { jQuery.ajax({ url: "../models/AjaxChecking.php", data: 'adminName=' + $("#adminName").val(), type: "POST", success: function(data) { $("#admin-availability-status").html(data); }, error: function() {} }); } < /script> 

 AjaxChecking <?php require_once'DB_Connection.php'; $obj_db=$this->obj_db(); if (!empty($_POST["adminName"])) { $query="SELECT count(*) FROM admins WHERE adminName='" . $_POST["adminName"] ."'"; $result=$obj_db->query($query); $row=mysql_fetch_row($result); $adminCount=$row[0]; if ($adminCount > 0) { echo"<span class='status-not-available'> $adminName Admin Name is already in use.</span>"; } else { echo"<span class='status-available'> $adminName Admin Name is Available.</span>"; } } ?> DB_connection <?php abstract class DB_Connection { protected function obj_db() { $host="localhost"; $user="root"; $password=""; $database="studentguidebook"; $obj_db=new mysqli(); $obj_db->connect($host, $user, $password); if($obj_db->connect_errno) { throw new Exception(" * DB Conenct Error - $obj_db->connect_error -$obj_db->connect_errno"); } $obj_db->select_db($database); if($obj_db->errno) { throw new Exception(" * DB Select Error - $obj_db->error -$obj_db->errno"); } return $obj_db; } } ?> 

 <div class="form-group mb-n"> <label for="largeinput" class="col-sm-2 control-label label-input-lg">Admin name</label> <div class="col-sm-7"> <input type="text" class="form-control1 input-lg" id="adminName" name="adminName" onBlur="checkAvailability()" placeholder="Enter Username ie Mast Be Unique" value="<?php echo($obj_admin->adminName); ?>"> </div> <div class="col-sm-3"> <p class="help-block" id="admin-availability-status"> <?php if (isset($errors[ 'adminName'])) { echo($errors[ 'adminName']); } ?> </p> </div> </div> 

Answer 1

在DB_connectio.php中，替换受公共保护的对象。

Answer 2

The goal of the abstract class is that you extend that class like this:

class myApp extends DB_Connection {

Then in one of the methods of your class (maybe the constructor) you can reference:

    $obj_db=$this->obj_db();

So you should look into making classes and separate model and view. Read about MVC (or similar patterns) to get going with that.

Now if you just want to have a quick-and-dirty solution, edit the DB_Connection script and turn it into a plain function:

function obj_db() {
   // ...
}

... so without the class wrapper. And then in your main script, just call it like this:

$obj_db=obj_db();

As said, this is quick-and-dirty. Over time, as your script will evolve you'll notice that there is a benefit in splitting up your code into modules, separating business logic from presentation and persistance. Classes and modules can help you to manage this. So then the first way is preferred.