Detailed explanation of code examples for buffer control in PHP

Everyone will inevitably use the header and setcookie functions when using PHP. These two functions will send a piece of file header information to the browser, but if there is any output before using these two functions ( Including empty output, such as spaces, carriage returns and line feeds) will prompt an error, the prompt information is as follows: "Header had all ready send by"! So is there any way to send the file header information after output? Several functions for buffer control have been added to PHP 4.0. Using these functions can help us solve many problems.
1. Introduction to related functions: ​
1. Flush: Output the content in the buffer and delete the buffer. Function format: flush() Description: This function is frequently used and is very efficient. ​ ​
2. ob_start: Open the output buffer ​ ​ Function format: void ​ ob_start(void) ​ ​ Description: When the buffer is activated, all non-file header information from the PHP program will not be sent, but will be saved in the internal buffer. In order to output the contents of the buffer, you can use ob_end_flush() or use ob_end_clean() to output the contents of the buffer. ​
3, ob_get_contents: Return the contents of the internal buffer. Usage: string ob_get_contents(void) Description: This function will return the contents of the current buffer. If the output buffer is not activated, it will return FALSE.
4. ob_get_length: Returns the length of the internal buffer. Usage: int ob_get_length(void) Description: This function will return the length in the current buffer; like ob_get_contents, if the output buffer is not activated. Returns FALSE. ​
5. ob_end_flush: Send the contents of the internal buffer to the browser and close the output buffer. Usage: void ob_end_flush(void) Description: This function sends the contents of the output buffer (if any).
6. ob_end_clean: Delete the contents of the internal buffer and close the internal buffer. Usage: void ob_end_clean(void). Note: This function will not output the contents of the internal buffer!
7. ob_implicit_flush: Turn on or off absolute refresh Usage: void ob_implicit_flush ([int flag]) Description: Anyone who has used Perl knows the meaning of $|=x. This string can open/close the buffer, and The ob_implicit_flush function is the same as that one. The default is to close the buffer and open absolute output.
2. Usage examples:
At the beginning, the author said that using buffer control functions can prevent errors in sending information in the file header. Here is an example:

 -------------------------------------------------------------     
    <?   //PHP提示符     
    ob_start();   //打开缓冲区     
    echo   "Hello/n";   //输出     
    header(&#39;location:gotourl.php&#39;);   
    //把浏览器重定向到gotourl.php     
    ?>    
     -------------------------------------------------------------

If ob_start is removed, PHP will prompt an error on line 4 of the file (the error message is as shown above), but if ob_start is added, no error will be prompted. The reason is that when the buffer is opened, the characters after echo will not be output. to the browser, but remains on the server. It will not be output until you use flush or ob_end_flush, so there will not be any file header output errors!
                                                                                                                                                                                are given below. What should I do if I want to save the output of the phpinfo() function? Before there was no buffer control, it can be said that there was no solution at all, but with buffer control, we can easily solve it:

 -------------------------------------------------------------     
    <?     ob_start();   //打开缓冲区     
    phpinfo();   //使用phpinfo函数     
    $info=ob_get_contents();   //得到缓冲区的内容并且赋值给$info     
    $file=fopen(&#39;info.txt&#39;,&#39;w&#39;);   //打开文件info.txt     
    fwrite($file,$info);   //写入信息到info.txt     
    fclose($file);   //关闭文件info.txt     ?>     
    -------------------------------------------------------------

Using the above method, just You can save the phpinfo information of different users, which I'm afraid there was no way to do before! In fact, the above is a method to convert some "processes" into "functions"!