Warning Cannot modify header information - headers already sent by ERROR

Question

I ve been struggling with this error for a while now   To start with  I just thought it was white space  but after further research I think it might be a problem similar to this      Look for any statements that could send output to the user before this header statement  If you find one or more  change your code to move the header statement before them  Complex conditional statements may complicate the issue  but they may also help solve the problem  Consider a conditional expression at the top of the PHP script that determines the header value as early as possible and sets it there    I m guessing the include header is causing the problem along with the header    but I m not sure how to rearrange the code to get rid of this error   How do I remove the error    lt  php      username    password    token    fName            include once  header php        if  isset   POST  username     amp  amp  isset   POST  password              username   sanitizeString   POST  username           password   sanitizeString   POST  password       Set temporary username and password variables      token      md5   password      Encrypt temporary password      if   username     admin                 header  Location summary php              elseif  username     admin                 header  Location admin php              elseif  username                      header  Location index php              else         die    lt body gt  lt div class  container  gt  lt p class  error  gt Invalid username or password  lt  p gt  lt  div gt  lt  body gt          if   username           token                      echo   lt body gt  lt div class  container  gt  lt p class  error  gt Please enter your username and password lt  p gt  lt  div gt  lt  body gt              else                query    SELECT   FROM members WHERE username   username AND password     token      Look in table for username entered          result   mysql query  query           if    result              die   Database access failed      mysql error             elseif  mysql num rows  result   gt  0                         row   mysql fetch row  result                 SESSION  username      username    Set session variables               SESSION  password      token                fName    row 0                     gt

User · Answer

Those blank lines between your   gt  and  lt  php tags are being sent to the client   When the first one of those is sent  it causes your headers to be sent first   Once that happens  you can t modify the headers any more   Remove those unnecessary tags  have it all in one big  lt  php block

User · Answer

This typically occurs when there is unintended output from the script before you start the session  With your current code  you could try to use output buffering to solve it   try adding a call to the ob start    function at the very top of your script and ob end flush    at the very end of the document

User · Answer

There is likely whitespace outside of your php tags

User · Answer

You are trying to send headers information after outputing content   If you want to do this  look for output buffering   Therefore  look to use ob start

User · Answer

There are some problems with your header   calls  one of which might be causing problems   You should put an exit   after each of the header  Location  calls otherwise code execution will continue You should have a space after the   so it reads  Location  http   foo  It s not valid to use a relative URL in a Location header  you should form an absolute URL like http   www mysite com some path php

User · Answer

Lines 45-47     gt    lt  php   That s sending a couple of newlines as output  so the headers are already dispatched  Just remove those 3 lines  it s all one big PHP block after all  no need to end PHP parsing and then start it again   as well as the similar block on lines 60-62  and it ll work   Notice that the error message you got actually gives you a lot of information to help you find this yourself      Warning  Cannot modify header   information - headers already sent by    output started at   C  xampp htdocs speedycms deleteclient php 47    in   C  xampp htdocs speedycms deleteclient php   on line 106   The two bolded sections tell you where the item is that sent output before the headers  line 47  and where the item is that was trying to send a header after output  line 106

User · Answer

Check something with echo  print   or printr   in the include file  header php   It might be that this is the problem OR if any MVC file  then check the number of spaces after   gt   This could also make a problem

User · Answer

Check the document encoding   I had this same problem  I develop on Windows XP using Notepad   and WampServer to run Apache locally and all was fine  After uploading to hosting provider that uses Apache on Unix I got this error  I had no extra PHP tags or white-space from extra lines after the closing tag   For me this was caused by the encoding of the text documents  I used the  Convert to UTF-8 without BOM  option in Notepad   under Encoding tab  and reloaded to the web server  Problem fixed  no code editing changes required

User · Answer

The long-term answer is that all output from your PHP scripts should be buffered in variables  This includes headers and body output  Then at the end of your scripts do any output you need   The very quick fix for your problem will be to add  ob start      as the very first thing in your script  if you only need it in this one script  If you need it in all your scripts add it as the very first thing in your header php file   This turns on PHP s output buffering feature  In PHP when you output something  do an echo or print  it has to send the HTTP headers at that time  If you turn on output buffering you can output in the script but PHP doesn t have to send the headers until the buffer is flushed  If you turn it on and don t turn it off PHP will automatically flush everything in the buffer after the script finishes running  There really is no harm in just turning it on in almost all cases and could give you a small performance increase under some configurations   If you have access to change your php ini configuration file you can find and change or add the following  output buffering   On   This will turn output buffering out without the need to call ob start     To find out more about output buffering check out http   php net manual en book outcontrol php

[php] Warning: Cannot modify header information - headers already sent by ERROR

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