llegal offset type errors occur when you attempt to access an array index using an object or an arrayas the index key.

Example:

$x = new stdClass(); $arr = array(); echo $arr[$x]; //illegal offset type

Your $xml array contains an object or array at $xml->entry[$i]->source for some value of $i, and when you try to use that as an index key for $s, you get that warning. You'll have to make sure $xml contains what you want it to and that you're accessing it correctly.