What does this error means?

[Shachar]

failed to open stream: HTTP wrapper does not support writeable connections 

And how do I fix it?
Happening when i'm trying to write to a file.

[Xelopheris]

The file isn't CHModed properly. You have to CHMod a file to at least 666 before PHP can write to it.

[Riklund]

how to chmod it with PHP.

This is an example of how to CHMOD a file with PHP:

// the file
$file = 'file_to_be_chmodded.txt';
// copy the old umask and set it to 0
$old_umask = umask(0);
// chmod the file
chmod($file, 0666);
// reset the umask
umask($old_umask); 

[Shachar]

I know how to CHMOD and the file was CHMODED just fine with 777 permissions. The problem was I should've used full directory path and not the URL of the file, I don't know exactly why, it should work both ways, but it solved it.

Thanks anyway guys

[Scott MacVicar]

using the URL of the file will force it to make a connection via HTTP which is slower than reading it from the file system.

[Shachar]

Thanks Scott