Use PHP to control the use of the user's browser-ob * function

Use PHP to control the use of the user's browser-ob * function
The Output Control function allows you to freely Control the Output of data in the script. It is very useful, especially when you want to output the file header after the data has been output. The output control function does not affect the header information sent using header () or setcookie (). It only applies to data blocks similar to echo () and PHP code.
Let's take a simple example to give you a general impression on Output Control:
Example 1.
<? Php
Ob_start (); // open the buffer
Echo "Hellon"; // output
Header ("location: index. php"); // redirects the browser to index. php.
Ob_end_flush (); // output all content to the browser
?>
Anyone who knows about the header () function knows that this function will send a file header to the browser, but if any output (including null output, for example, a blank space, carriage return, or line feed will prompt an error. If we remove ob_start () from the first line and execute this program, we will find an error message: "Header had all ready send "! However, when ob_start is added, no error will be prompted because when the buffer zone is opened, the characters after echo will not be output to the browser, but will be retained on the server until you use flush or ob_end_flush, so there will be no file header output errors!
1. Related functions
1. Flush: refresh the buffer content and output it.
Function format: flush ()
Note: This function is frequently used and highly efficient.
2. ob_start: Open the output buffer.
Function format: void ob_start (void)
Note: When the buffer zone is activated, all non-file header information from the PHP program is not sent, but stored in the internal buffer zone. To output the buffer content, you can use ob_end_flush () or flush () to output the buffer content.
3. ob_get_contents: returns the content of the internal buffer.
Usage: string ob_get_contents (void)
Note: This function returns the content in the current buffer. If the output buffer is not activated, FALSE is returned.
4. ob_get_length: return the length of the internal buffer.
Usage: int ob_get_length (void)
Note: This function returns the length of the current buffer. It is the same as ob_get_contents if the output buffer is not activated. Returns FALSE.
5. ob_end_flush: sends the content of the internal buffer to the browser and closes the output buffer.
Usage: void ob_end_flush (void)
Note: This function sends the content of the output buffer (if any ).
6. ob_end_clean: delete the content of the internal buffer and disable the internal buffer.
Usage: void ob_end_clean (void)