fixes and doc comments

Author: Girgias

ext/pgsql/pgsql.c

@@ -3879,6 +3879,11 @@ static void php_pgsql_do_async(INTERNAL_FUNCTION_PARAMETERS, int entry_type)
 	switch(entry_type) {
 		case PHP_PG_ASYNC_IS_BUSY:
 			PQconsumeInput(pgsql);
+			/* PQisBusy
+			 * Returns 1 if a command is busy, that is, PQgetResult would block waiting for input.
+			 * A 0 return indicates that PQgetResult can be called with assurance of not blocking.
+			 * https://www.postgresql.org/docs/current/libpq-async.html#LIBPQ-PQISBUSY
+			 */
 			RETVAL_BOOL(PQisBusy(pgsql));
 			break;
 		case PHP_PG_ASYNC_REQUEST_CANCEL: {
@@ -3887,10 +3892,15 @@ static void php_pgsql_do_async(INTERNAL_FUNCTION_PARAMETERS, int entry_type)
 			int rc;
 
 			c = PQgetCancel(pgsql);
-			rc = PQcancel(c, err, sizeof(err);
+			rc = PQcancel(c, err, sizeof(err));
+			/* PQcancel
+			 * The return value of PQcancel is 1 if the cancel request was successfully dispatched and 0 if not.
+			 * If not, errbuf is filled with an explanatory error message.
+			 * errbuf must be a char array of size errbufsize (the recommended size is 256 bytes).
+			 * https://www.postgresql.org/docs/current/libpq-cancel.html#LIBPQ-PQCANCEL
+			 */
 			RETVAL_BOOL(rc);
-			if (rc < 0) {
-				RETVAL_FALSE;
+			if (rc == 0) {
 				zend_error(E_WARNING, "cannot cancel the query: %s", err);
 			}
 			while ((pgsql_result = PQgetResult(pgsql))) {