PHP+ closes the output stream: an important measure to ensure the safety of program operation

In the PHP development process, security has always been an issue that we have to pay attention to. When writing programs, we often use various means to prevent hacker attacks and ensure user data security. Closing the output stream is one of the most commonly used security measures.

1. What is closing the output stream

In PHP programs, the output content is often output to the client's browser or other terminal through functions such as echo, print, var_dump, etc. Closing the output stream means closing the output stream while the program is running, thereby preventing unnecessary error messages and even malicious code from being output to the browser and enhancing the security of the program.

2. Why should we close the output stream?

1. Prevent being attacked by hackers

When the output stream is not closed, some attackers may pass The URL injects some malicious code to obtain important user information, modify data, etc. However, if the output stream is closed, hackers will not be able to obtain the output information of the application and will not be able to exploit these vulnerabilities.

2. Prevent leakage of project information

Sometimes we will include sensitive information in the output, such as database configuration, bug information, etc. For an attacker, this information can become a weak point in the attack, so closing the output stream can protect the security of the system and prevent the leakage of important information.

3. Improve program performance

Closing the output stream can reduce the amount of data output by the system, thereby increasing the running speed of the program and reducing the burden on the server. This is especially important for programs with large access volumes or long running cycles.

3. How to close the output stream

PHP provides a variety of methods to close the output stream. We will introduce them separately below.

1. Method 1: Using the php.ini file

In the php.ini configuration file that comes with PHP, there is a configuration item: output_buffering. If this value is set to On, all output of the program will be written to the cache first and will not be output until the script is executed, which is equivalent to closing the output stream. This can be achieved by adding the following lines of code to the PHP configuration file:

output_buffering = On;
output_handler = ob_gzhandler;

2. Method 2: Use the PHP built-in function ob_start()

This function can open an output buffer and stuff all program output into this buffer. After execution, the buffer can be emptied and the entire contents of the program can be output. When clearing this buffer, you can choose the following two methods:

flush(): directly output the buffer content, and then clear the buffer.
ob_end_flush(): This function will first output all the contents of the buffer and then clear the buffer.

The following is a code example:

ob_start();
echo "Hello, world!";
$output=ob_get_contents(); / /Get the data in the buffer, but do not clear the buffer
ob_end_clean(); //Clear the buffer pool
echo $output;
?>

3. Method three: Using PHP's built-in function header()

header() function is often used to send HTTP header information to the browser, but it can also be used to close the output stream. In actual development, there are two ways to achieve this:

header("Content-type: text/html; charset=utf-8");
header("HTTP/1.1 200 OK") ;
header('Content-Length: 0');

Or:

header("HTTP/1.1 200 OK");
header('Connection: close' );//Close the connection

4. Method 4: Using the Apache/nginx configuration file

In the Apache server, we can close the output stream by modifying the .htaccess file the goal of. In the nginx server, we can achieve this through configuration files.

Add the following code in the .htaccess file:

php_value output_buffering On;

Add the following content in the nginx configuration file to achieve configuration:

location ~ .php$ {

fastcgi_pass   127.0.0.1:9000;
fastcgi_param  SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_buffer_size 4k;
fastcgi_buffers 4 4k;
fastcgi_busy_buffers_size 8k;
fastcgi_read_timeout 300;
fastcgi_send_timeout 300;
fastcgi_connect_timeout 300;
fastcgi_buffering on; #开启缓冲池

}

4. Notes

1. During development, you need to carefully consider whether you need to close the output stream. If it is overused, it may It will bring certain difficulties to project maintenance.

2. Closing the output stream needs to be done at the entry of the program, otherwise the security of the program cannot be guaranteed.

3. Closing the output stream may have a certain impact on the performance of the program and needs to be considered comprehensively.

In short, closing the output stream is one of the important measures to ensure the safety of PHP program operation. Developers need to fully understand its principles and implementation methods, and flexibly apply it in actual projects to ensure the security of user data.

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