problem writing a plugin

hey friends,

I am writing a plugin which reads remote url. Can anybody read my code n explain wht is the change that i need to make.

following is the error
Warning: Cannot modify header information – headers already sent by (output started at E:\xampp\htdocs\id8labs\wp-content\plugins\retrieve-business-data\retrieve-business-data.php:13) in E:\xampp\htdocs\id8labs\wp-content\plugins\retrieve-business-data\retrieve-business-data.php on line 76

on Line 76 following is the code

header(“Location: $PHP_SELF”);
exit();