This misstep in like manner presents as "Can't modify header information" dependent upon the PHP version. This article helps you to find the information of  Warning: Cannot Modify Header Information.

To lay it out simply, it infers that some spot in the code, something was printed to the program before Drupal had wrapped up setting up the page. This is consistently achieved by custom or modified code contributed from sources outside Drupal, so audit your exceptionally added code (tallying subjects) first. 

If you get a "Headers recently sent" botch, there are three likely causes. 

Expecting this mix-up isn't the essential bumble message on the page, it is altogether likelihood a 'heavy slide sway' of past goofs and you may neglect it. Taking everything into account, base on fixing the mix-ups before it. Right when you fix the principle botch message(s), the "Headers recently sent" error(s) will presumably disappear. 

Word processors to a great extent install a UTF-8 byte demand mark at the most noteworthy place of a report. For the present circumstance, the slip-up message will customarily say that "yield started" at line 1 of some archive. To fix this, plan your substance supervisor to save the archive without a byte demand mark. 

Regardless, if you get a slip-up "Headers recently sent" as the primary bumble and it uncovers to you the slip-up is near the uttermost furthest reaches of an archive (check which record "yield started at" centers too), that most probable infers that there are extra territories or lines after an end ?> PHP tag. In Drupal coding rules, it is unequivocally proposed (for this very clarification) that PHP records should not have any end ?> tags. Delete them, and everything should end up incredible. 

Extra whitespace being added undoubtedly is achieved by a horrible dumping program or conceivably a defiant administrator (Windows Notepad or Wordpad, Mac TextEdit) adding it. 

Issues with "headers recently sent" can moreover be achieved by having an unmistakable line after *.inc archives. Drupal or more likely PHP seems to have issues with extra territories generally. 

Check all *.inc records to guarantee there are no closure PHP ?> tags in any of them. Closing PHP ?> tags are not needed in your *.inc reports. Moreover, check all *.php records to guarantee there are no reasonable lines at the beginning of the completion of the report. 

If the bungle message exhibits that this is achieved by a module, incapacitate modules separately to find which one is causing the issue. 

This can moreover be achieved by UTF-8. If a site is coded in ASCII and PHP archives are being saved as UTF-8, it can cause this message. If the site and DB are both UTF-8, it should be okay to save PHP records as UTF-8. 

Likewise, this goof message is related to the "output_buffering" variable in php.ini. If output_buffering is set to some store, the specialist will send headers with deferral (or change them not long after they are sent), and this screw-up will not be staggered. However, accepting output_buffering is set to 0 or not in the smallest degree, headers can be sent at simply a solitary second and, if there's a terrible code, it will trip this mix-up message. To sum up, turning on the "output_buffering" variable in php.ini fixes this issue.