标头已发送警告使用Google Analytics实验代码[重复]

Question

This question already has an answer here:

• How to fix “Headers already sent” error in PHP 11 answers

I am getting the error WARNING, headers already sent,

for some reason it says the output started at the end of the google analytics tracking code for google experiments I had,

the full file of that file is this

<!-- Google Analytics Content Experiment code -->
<script>function utmx_section(){}function utmx(){}(function(){var
k='62393235-4',d=document,l=d.location,c=d.cookie;
if(l.search.indexOf('utm_expid='+k)>0)return;
function f(n){if(c){var i=c.indexOf(n+'=');if(i>-1){var j=c.
indexOf(';',i);return escape(c.substring(i+n.length+1,j<0?c.
length:j))}}}var x=f('__utmx'),xx=f('__utmxx'),h=l.hash;d.write(
'<sc'+'ript src="'+'http'+(l.protocol=='https:'?'s://ssl':
'://www')+'.google-analytics.com/ga_exp.js?'+'utmxkey='+k+
'&utmx='+(x?x:'')+'&utmxx='+(xx?xx:'')+'&utmxtime='+new Date().
valueOf()+(h?'&utmxhash='+escape(h.substr(1)):'')+
'" type="text/javascript" charset="utf-8"><\/sc'+'ript>')})();
</script><script>utmx('url','A/B');</script>
<!-- End of Google Analytics Content Experiment code -->

why would I be getting this error?

</div>

Answer 1

No output should be above the headers. There is a range of reasons why this could be caused. examples.

<?php
header ("Location: test.php");
?>

this wont throw an error

<?php
 echo "blabla";
header ("Location: test.php");
?>

OR

<strong> test</strong>
<?php
header ("Location: test.php");
?>

the above will trigger an error.