How to use PHP to implement mobile adaptation

With the popularity of smartphones, the demand for mobile websites is becoming more and more urgent. However, due to the various screen sizes and resolutions of mobile devices, it is more difficult to develop mobile websites. How to achieve adaptive adaptation has become one of the problems faced by developers. This article will introduce how to use PHP to implement mobile terminal adaptation.

1. Introduction to the mobile terminal adaptation scheme

In the mobile terminal adaptation scheme, there are currently three main methods:

1. Manually set the viewport

By manually setting the viewport, the page can be freely scaled according to the screen size of the device. At the same time, the layout of the page also needs to be changed. For example, when designing a fixed-width container, you need to set its width as a percentage or rem.

2. Media query

Media query is also a popular mobile adaptation solution. By detecting the device's resolution, the page layout is changed based on the device's size and viewport. However, the disadvantage of this method is that it requires writing a lot of CSS code and the maintenance cost is high. At the same time, the size of the CSS file will also increase, affecting the loading speed of the page.

3. Using CSS preprocessor

The CSS preprocessor can generate CSS code that adapts to devices with different resolutions. For example, you can use Sass to generate CSS code for devices with different resolutions. However, this method requires you to install the CSS preprocessor first, and you also need to master how to use it. It is difficult for some novices.

2. PHP-based adaptation solution

PHP is a popular server-side language that can generate dynamic HTML pages. In the mobile terminal adaptation solution, we can use PHP to dynamically generate HTML code that adapts to different devices. The specific implementation is as follows:

1. Set the viewport meta tag

Add the following content to the PHP code to set the viewport tag so that the page can automatically scale to the width of the device.

<meta name="viewport" content="width=device-width,initial-scale=1.0,maximum-s```

2.判断移动设备

我们可以使用PHP的$_SERVER['HTTP_USER_AGENT']变量来判断当前设备是否为移动设备。根据不同的设备类型加载不同的CSS文件或者JS文件。

例如，对于移动设备，我们可以使用以下代码引入移动端CSS文件。

if (preg_match('/(iphone|ipod|ipad|android)/i', strtolower($_SERVER['HTTP_USER_AGENT']))) {
echo '';
}

对于PC端设备，我们可以使用以下代码引入PC端CSS文件。

if (!preg_match('/(iphone|ipod|ipad|android) /i', strtolower($_SERVER['HTTP_USER_AGENT']))) {
echo '' ;
}

3.响应式图片

对于移动设备，我们可以使用响应式图片来适配不同的屏幕。通过以下代码来实现：

         image_medium.jpg 640w,
         image_large.jpg 1200w"
 sizes="100vw"
 alt="responsive image">

Copy after login

以上代码会根据不同的设备加载不同的图片。

4.封装函数

为了方便使用和维护，我们可以使用PHP封装函数来实现适配功能。例如，我们可以使用以下代码来加载不同设备下的CSS文件。

function getCSS($url_mobile, $url_pc)
{

$agent = strtolower($_SERVER['HTTP_USER_AGENT']);
$is_mobile = (strpos($agent, 'mobile') !== false || strpos($agent, 'android') !== false);

echo '<link rel="stylesheet" type="text/css" href="' . ($is_mobile ? $url_mobile : $url_pc) . '" />';

}

以上代码会根据当前设备加载不同的CSS文件。我们可以在代码中调用getCSS函数来实现适配。

getCSS('css/mobile.css', 'css/pc.css');

三、总结

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