binary cursor returning truncated data

Hello,

i am trying to retrieve binary content of a bytea field (or postgis geometry field) with a binary cursor with PHP :

$sql="BEGIN;DECLARE mycursor BINARY CURSOR FOR SELECT shape FROM $layerName; fetch all in mycursor;"
....pg_query...

But my shape field shows only two bytes of data.

Does someone know if it is a current PHP restriction ?

Thanks by advance,

Eric