SQL escape string function

Escapes special characters in a string for use in an SQL statement. howewer it check get_magic_quotes_gpc function is enable or no. if true , it strips string from slashes and escaped string from special characters in a string for use in an SQL statement.

function sql_escape_string( $str, $conn = '' )
{
   if ( get_magic_quotes_gpc() )
      $str = stripslashes( $str );
   //check if this function exists
   if ( function_exists( "mysql_real_escape_string" ) and $conn )
      $str = mysql_real_escape_string( $str, $conn );
   else
      $str = addslashes( $str ); //for PHP version < 4.3.0 use addslashes
   return $str;
}