# QA Official

### Netty Getting Started to Proficient Courses | Internet of Things Video Course

https://qaofficial.com/post/2019/04/24/68722-netty-getting-started-to-proficient-courses-internet-of-things-video-course.html 2019-04-24
《Netty Introduction to Core Technologies of Internet of Things to Proficient Courses》 本课程由www.51education.net独家提供 课程来源于： http://www.xuetuwuyou.com/course/14 课程内容介绍： 一、课程用

### PCA Understanding Ideas

https://qaofficial.com/post/2019/04/24/68763-pca-understanding-ideas.html 2019-04-24
PCA has a lot of information on the Internet. People may read what Daniel wrote on the Internet about principles. I am only writing a basic understanding here.Mainly refer to the great god of information, https://zhuanlan.zhihu.com/p/21580949 PCA is mainly to find the eigenvector corresponding to the eigenvalue with the largest covariance matrix of the data set, thus finding the directions with the largest variance of the data, achieving the effect of dimension reduction for the data, reducing a vector with n dimensions to d dimensions, where d < n.

### ajax post Request Method

https://qaofficial.com/post/2019/04/24/68537-ajax-post-request-method.html 2019-04-24

### js native and ajax get and post methods and jsonp native writing

https://qaofficial.com/post/2019/04/24/68560-js-native-and-ajax-get-and-post-methods-and-jsonp-native-writing.html 2019-04-24
login.onclick = function(){var xhr = new XMLHttpRequest();xhr.open("get","http://localhost/ajax2/test2.php?username="+username.value+"&pwd="+pwd2.value,true);xhr.send();xhr.onreadystatechange = function(){if (xhr.readyState == 4) {if (xhr.status>=200 && xhr.status<300) {alert(xhr.responseText);};};} } ajax method btn.onclick = function(){ajax( "GET", "http://localhost/ajax2/my02.php", {xingming:xingming.value,pwd:pwd.value}, function(data){console.log(data);},function(errCode){console.log(errCode);}) post Method Pass Parameters It differs from a get method: 01 safety type.Post is safer.The speed of get is 0.3 order of magnitude faster.Post is of a larger order of magnitude. Specific Implementation: var xhr = new XMLHttpRequest();

### tp5 how to judge the request method, tp5 request method summary judgment ajax submission

https://qaofficial.com/post/2019/04/24/68568-tp5-how-to-judge-the-request-method-tp5-request-method-summary-judgment-ajax-submission.html 2019-04-24

### upper_bound () and low_bound functions

https://qaofficial.com/post/2019/04/24/68629-upper_bound-and-low_bound-functions.html 2019-04-24
prerequisite: a non-descending sequence!!!!!! lower_bound () function uses: Its parameters are: 1. Address of an array element (or array name to represent the first address of the array, to represent the address of the element to be compared at the beginning of the array, not necessarily the first address, but only the " first" address to be compared), 2. The address of an array element (corresponding to the address of

### yii2 ajax post submission problem

https://qaofficial.com/post/2019/04/24/68556-yii2-ajax-post-submission-problem.html 2019-04-24
The first solution is to turn off Csrf 1, partially closed: publicfunctioninit () { $this-> enablecsrfvalidation = false;} 2, global shutdown: in the configuration file (main-local.php or web.php), set to " enablecsrfvalidation" = > false,//true to turn on csrf validation The second solution is to add hidden fields to the form form;Name="_csrf " is the default configuration for the framework <input name="_csrf" type="hidden" id="_csrf" value="<?= Yii::$app->request->csrfToken ?