Help with The Wire and Appending PHP

So, i have a problem.

I'm desenvolving a social network and i need that the elgg, take what was posted on the wire and save this in a append php.

 

here, i have an example of append php:

$file="arquivo.txt";
$content="something";
file_put_contents($file,$content,FILE_APPEND);

 

at this example, the php save in the "arquivo.txt" what is in content (in this case, "something"). But i need that elgg, on the place of "something" write what was posted on the wire, for any user. thanks for the help