How to close buffer in php

php method to close the buffer: 1. Open the PHP installation directory, find and open the configuration file "php.ini"; 2. In the configuration file, find the "output_buffering" item, and set the value of this item Just set it to "Off".

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

PHP buffer ( buffer)

The script output information is first put into the buffer. Only when the buffer is full or the script is finished running, the data will be transferred to the next stage. You can find the output_buffering setting item in the configuration file php.ini. My default configuration (Windows/XAMPP v3.2.2) is 4096

If set to On, the buffer is available and has no size limit;

If set to Off, the buffer is unavailable;

If set to an integer, the buffer The area is available and is the set size, in bytes.

It should be noted that ini_set cannot set the buffer size. When initializing the script running environment, the buffer has been defined; in cli mode, the default output_buffering is Off. .

Then the question is, what is the difference between closing and opening the buffer? What does the initial buffer size do? The cli mode is turned off by default. Can it be turned on if business needs it? What are the benefits of the cache area?

1. What is the difference between closing and opening the buffer?

Pass code inspection

When output_buffering is configured as 4096, run the code

Output result: After waiting for 3 seconds , output start and end at the same time

When Output_buffering is configured as Off, run the same code

The output result: start is output first, and after waiting for 3 seconds, end

## is output #Looking at it alone, the results are exactly the same~ But observing its operation process, I found surprising differences. If buffering is turned off, "start" is output first, and then "end" is output after waiting for 3 seconds. When the buffer is turned on, it will wait for the script execution to complete and output the results together

In this example, flush is used to refresh the apache buffer, similar to allowing the PHP buffer to establish a direct connection with the browser, so that our attention Be able to focus on the PHP buffer itself.

Through a vivid example, PHP's buffer is like a big house. Every time the output function such as echo is executed, the data is thrown into this big house until the script execution is completed or the ob_flush function is executed. The data is released from the big house and thrown into the WebServer buffer. After closing the PHP buffer, the echo function is executed. What should I do if there is no big house to put it in? I have to hand it over directly to the WebServer buffer.

Through examples and code execution results, we can understand that the so-called PHP buffer is a data storage hub developed by PHP itself, and a series of ob functions operate for this purpose. (Cite a few example functions)

ob_clean();                         //Delete the contents of the internal buffer, do not close the buffer (no output).

ob_end_clean(); //Delete the contents of the internal buffer and close the buffer (no output).

ob_get_contents(); //Returns the contents of the buffer, does not output

ob_get_length(); //Returns the length of the internal buffer. If the buffer is not activated, this function returns FALSE .

2. What is the role of the initial buffer size?

Change output_buffering from 4096 to 5 to facilitate test execution

Execution code

Output description: After waiting for 3 seconds , output 1234end

Execution code

Output description: Output 12345, wait for 3 seconds, output end

By comparison of the output, It explains the difference very well.

The buffer can only hold 5 bytes of data. If the data is less than the maximum value, it can be stored first. If it is greater than or equal to the critical value, the data will have to be kicked out. This is the same as We manually executed an effect of the ob_flush function.

3. The cli mode is turned off by default. Can it be turned on if business needs it?

This question can be supplemented. In non-cli mode, if php.ini sets the buffer to be closed, but the business needs to use the buffer, what should I do? Is it possible to change the configuration? Of course it won't be that difficult. At this time, another ob function comes,

ob_start(); //Open an output buffer. All output information is no longer sent directly to the browser, but saved inside the output buffer.

Now that we know that PHP buffer is similar to the concept of temporary data storage area, let’s go back and look at the TP5 source code.

Let’s first look at the explanation of ob_get_level and ob_get_clean functions

ob_get_level(): Returns the nesting level of the output buffering mechanism.

ob_get_clean(): Get the contents of the current buffer and delete the current output buffer.

We can also learn a thing or two from the code. If the level is greater than 0, get the contents of the buffer and delete the buffer, and then open a new one through ob_start. This is also in line with the instructions in the comments. "reapply".

The so-called nesting is explained here. As for when the value of level will be 0, and what is it if it is non-0, please turn off php.ini output_buffering and output to see the result. In addition, ob_start multiple times and ob_get_level multiple times, let’s try to compare the output results.

Let’s take a look at the two models first

##When ob_start opens a new buffer multiple times , the data structure is constructed as the second type, which is nesting. ob_get_level returns the nested level.

My personal understanding is that nesting can be compared to Java's stream mechanism. The data in one buffer is output to the next buffer, and then customized operations can be performed on the data.

Now looking at the TP5 source code, the idea is clearer. If the system initializes the buffer, delete it first and then reopen it because the size may be limited. The size of the cache area opened by executing ob_start is "big enough", but there is no specific explanation of how big it is. I only know that no matter how big the written data is, it will not be sent until the end of the script

4. What are the benefits of the cache area?

PHP output data is sent to WebServer. If echo is executed and sent once, this increases resource consumption. It is more efficient to store it in memory and send it uniformly.

Web requests contain HTTP headers, and there must be no output before the headers are set. The PHP buffer does this work for us, outputting various data before sending the header. The buffer will first send the header information to WebSever, and then send the data packets uniformly.

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