Warning: Cannot modify header information

Not being a php wizard I sorta freak out when I see odd messages like:

Warning: Cannot modify header information…

But never fear google is here. A quick lookup through a few posts reveals that this is caused by adding whitespaces, specifically the line breaks, into places inside of a php file where they should be. This is because the line breaks in files are actual code that php gets stupid all over. The two main culprits are at the beginning or the end of a file.

Cheers