First : Echo before header
<?php
echo "hello world"
...
header('Location: http://...');
?>
Solution:
Remove the echo before header
Use ob_start(); and ob_end_flush(); for buffered output
Second : New-line characters or spaces before <?php
<?php
... header('Location: http://...');
?>
Solution:
Remove everything before <?php
Third : Header Location in mixed php/HTML
<html>
...
<body>
...
<?php header('Location: http://...'); >
...
</body>
</html>
Solution:
You cannot use header-location here, because the header and the HTML code have already been sent!
Forth : Empty lines, chars or spaces after ?> when using an php include file
<?php ... ?> ... ...
Solution:
Remove everything after ?> in the php include file
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