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Code for buffer control in PHP_PHP tutorial
- WBOYOriginal
- 2016-07-20 11:16:19755browse
When you use PHP, you will inevitably use the header and setcookie functions. These two functions will send a piece of file header information to the browser, but if you already have it before using these two functions Any output (including empty output, such as spaces, carriage returns and line feeds) will prompt an error, with the following message: "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()
Note: This function is frequently used and is very efficient.
2. ob_start: open the output buffer
Function format: void ob_start(void)
Note: 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: Returns 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; the same as ob_get_contents, if the output buffer is not activated. then 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])
Note: 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. 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.
Example:
ob_start(); //Open buffer
echo "Hello/n"; //Output
header('location:gotourl.php'); //Redirect the browser to gotourl.php
//edit: www.jbxue.com
?>>If ob_start is removed, PHP will prompt an error on line 4 of the file (the error message is as shown above), but with ob_start, no error will be prompted. The reason is that when the buffer is opened, the characters after echo It will not be output to the browser, but will be retained 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!
The following is a very classic use:
For example, you use to get the setting information of the server and client, but this information will be different depending on the client. What if you want to save the output of the phpinfo() function? Before there was no buffer control, it can be said that there was no way at all, but with buffer control, we can easily solve it:
Using the above method, you can save the phpinfo information of different users. This may not have been possible before! In fact, the above is a method to convert some "processes" into "functions"!