Steps to build a single-page application (SPA) using PHP: Create a PHP file and load Vue.js. Define a Vue instance and create an HTML interface containing text input and output text. Create a JavaScript framework file containing Vue components. Include JavaScript framework files into PHP files.

The form tag is used to create a form that allows users to enter data and submit it to server-side processing. Attributes include action (handler URL), method (submission method), name (form name), target (submission target), enctype (data encoding method). Form elements include text boxes, drop-down lists, text areas, buttons, etc. Submitting the form will send the data to the server via the specified method and URL.

The method of using layui to transmit data is as follows: Use Ajax: Create the request object, set the request parameters (URL, method, data), and process the response. Use built-in methods: Simplify data transfer using built-in methods such as $.post, $.get, $.postJSON, or $.getJSON.

Adaptive layout can be achieved by using the responsive layout function of the layui framework. The steps include: referencing the layui framework. Define an adaptive layout container and set the layui-container class. Use responsive breakpoints (xs/sm/md/lg) to hide elements under specific breakpoints. Specify element width using the grid system (layui-col-). Create spacing via offset (layui-offset-). Use responsive utilities (layui-invisible/show/block/inline) to control the visibility of elements and how they appear.

In Vue.js, event is a native JavaScript event triggered by the browser, while $event is a Vue-specific abstract event object used in Vue components. It is generally more convenient to use $event because it is formatted and enhanced to support data binding. Use event when you need to access specific functionality of the native event object.

DOM (Document Object Model) is an API for accessing, manipulating and modifying the tree structure of HTML/XML documents. It represents the document as a node hierarchy, including Document, Element, Text and Attribute nodes, which can be used to: access and modify Document structure Access and modify element styles Create/modify HTML content in response to user interaction

Layui is based on HTML, CSS, JavaScript, jQuery, Less and Grunt technologies and offers cross-browser compatibility, high customizability, ease of use, rich components and active community support.

There are two ways to set the background image in layui: using CSS style: body { background-image: url("path/to/image.jpg"); } using layui API: layui.use('element', function() { element.addStyle('.layui-body{background-image: url("path/to/image.jpg");}') });