Warning: cannot send session cookie-headers already sent

Warning cannot send session cookie-headers already sent... Problem Solving (problem caused by UTF-8 BOM of PHP)

I am used to using edit plus for PHP programming, so sometimes some unknown errors may occur, which is very troublesome;
Recently, the following problems always occur on some pages during project development:

Warning: session_start () [function. session-start]: cannot send session cookie-headers already sent by (output started at E:/web/apache2/htdocs/index. PHP: 1) in E:/web/apache2/htdocs/functions/sessions. PHP on line 67

Warning: session_start () [function. session-start]: cannot send session cache limiter-headers already sent (output started at E:/web/apache2/htdocs/index. PHP: 1) in E:/web/apache2/htdocs/functions/sessions. PHP on line 67
After detailed search, the following causes are obtained:
In my edit plus settings, the default encoding is UTF-8, And the utf_8 signature is: always add a signature;
Therefore, try the following operations:
In the edit plus tool> parameter> File> utf_8 signature, change the option "always add signature" to "always remove signature" and open index. PHP file, save it as a new one, and re-run the script, and finally it will work properly;

In addition, I found two useful articles on the Internet. I hope someone can solve this problem perfectly!

A UTF-8 BOM caused by PHP strange problem I,

// --- A. php
<? PHP
Header ("Content-Type: image/BMP ");
Session_start ();
................
?>
Save a. php as UTF-8. the following error occurs when you access the PHP file in a browser:
Warning: session_start () [function. Session-start]: cannot send session cache limiter-headers already sent (output started

At ×××. php: 1) In ××× on line 2

This problem is common, most of which are output before session_start! For laruence, this error basically does not happen, but if you use DW or editplus

This error may occur even if you are a programmer writing code!

As shown in the preceding figure, there are no output statements in line 2 of the XXX file and line 2 of the XXX file, it's strange. Why?
Originally:

Unicode signature (BOM) can include the byte sequence mark (BOM) in the document ). Bom is two to four bytes at the beginning of a text file. It can be identified as Unicode.

The byte sequence of the subsequent bytes. Because the UTF-8 does not have a byte order, you can choose to add a UTF-8 Bom. This is required for UTF-16 and UTF-32.
No! If this option is selected, 2 to 4 bytes will be output at the beginning of the page!

Session_start () requires no output to the client browser before.

II,

Another error may occur, for example:
/-- A. php --
?>
Empty row
Empty row

This problem also occurs when you include a. php files. We recommend that you do not include the files that are often included at the end?>

Another example:
No output is allowed before session_start () is called. For example, the following is an error.
Incorrect.
========================================================== =
1 line
2 rows <? PHP
3 rows session_start (); // output already exists in the first row
4 rows .....
5 rows?>
========================================================== =

It is indeed so strange that it has been tested.
III,

Session_start ()
Set_cookie ()
Header ()
The preceding @ should be used to suppress this warning.

IV,

In the editplus Editor, If you first convert the. php file of UTF-8 to gb2312 or another file, and then convert it to UTF-8, the file can be accessed successfully, that is

Bom is removed, at this time the UTF-8 is no Bom type

Php-session_start () error caused by UTF-8 encoding

14:55:01

Large, medium, and small
The default gb2312 encoding is compatible with ANSI encoding. the file header does not have any additional information. In this case, session_start () can work properly.
When UTF Encoding is used, most editors will append a BOM block to the file header. My editplus appends FF Fe and uses a hexadecimal editor.
You can see clearly. In this way, when session_start () is called, two bytes are actually output to the browser, except that the hidden characters are
The following warning is displayed in the browser:
Warning: session_start () [function. session-start]: cannot send session cookie-headers already sent by (output started ......................

Solution:
1. Manually remove the BOM block. You can edit it in a hexadecimal Editor, such as ultraedit, or use the built-in functions of the editor. A good editor generally provides the option of removing the BOM block.
2. Write a script to correct it. For different editors, the BOM header is defined as follows:
UTF-8 EF BB BF
UTF-16 big endian Fe FF
Little endian FF Fe UTF-16
UTF-32 big endian 00 00 Fe FF
UTF-32 little endian FF Fe 00

Solution

During the PHP session operation, if the following error occurs: Warning: cannot send session cookie-headers already sent... "or" cannot add header information-headers already sent ..."

You only need to set output_buffering in PHP. ini. The default value is no. You can change this value to 1.