PHP uses ob_start() to explain the method of clearing output and selective output

The editor below will share with you an article on how to use ob_start() in PHP to clear output and selective output. It has a good reference value and I hope it will be helpful to everyone. Let’s follow the editor and take a look.

1. Background

There is a piece of code. Because the encapsulated method is called, there will be some The return value is not needed. How to deal with these return values ​​​​to make them disappear. Some people will say, wouldn't it be better to clear the variables? But what if this return value cannot be cleared?

2. ob_start()

1. Concept:

This function will open the output buffer. When output buffering is activated, the script will not output content (except http headers), instead the content to be output is stored in an internal buffer.

The contents of the internal buffer can be copied to a string variable using the ob_get_contents() function. To output the contents stored in the internal buffer, use the ob_end_flush() function. In addition, using the ob_end_clean() function will silently discard the contents of the buffer.

From php manual: http://php.net/manual/zh/function.ob-start.php

2. Basic usage of buffer

//打开缓冲区
ob_start();
//清除缓冲区中的内容
ob_clean();
//冲刷出（送出）输出缓冲区内容并关闭缓冲
ob_end_flush();

##3. Basic testing

1、

echo '1';
ob_start();
echo '2';
ob_clean();

Result: 1

Explanation: This is the simplest usage, that is, add ob_start(); to the outside where you don’t want to output content. Then clear the content in the buffer, thus realizing our usage scenario. We can selectively output what we want to output. Get rid of what you don't want to output.

2,

echo '1';
ob_start();
echo '2';
//输出缓冲区
ob_end_flush();

Result: 12

3,

//打开缓冲区
ob_start();
echo '1';
//清除缓冲区，此时不会输出1
ob_clean();
//输出缓冲区。但是因为上面已经清除过缓冲区了，所以不会输出 1
ob_end_flush();
echo '2';

Results: 2

#4,

ob_start(); //打开缓冲区
echo '1'; 
$a = ob_get_contents(); //输出缓冲区内容到$a,相当于赋值给$a
ob_clean();   //这里清除缓冲区内容
echo '2';    //输出2
echo $a;    //输出$a

Result: 2 1

Explanation: ob_get_contents(); here is to get the contents of the buffer. We can assign the obtained content to a variable, so that even if the buffer is cleared and we output the variable, we can still output 1 normally.

4. Commonly used places

This function is commonly used for page staticization. It plays a key role in constructing a micro web framework. The rendered page is directly written to a file through the input cache. In this way, it can be judged whether the file exists to determine whether the user needs to re-render a page during this visit. It can also be applied to large projects and use nosql to store it. The specific usage of the rendered page varies from person to person, it depends on which one you like

The above is a simple test I did myself. If necessary, you can refer to the PHP manual and do more tests.

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