Compilation error: How to use php stream APIs in a php extension

hi, i'm trying to develop a php extention. it need to be able to read php file streams. when i'm trying to make php with my extension, i'm getting this error : (from "make") ext/fpdf/f_stream_php.o(.text+0x2c0): In function `f_stream_file::size()': : undefined reference to `_php_stream_tell(_php_stream*)' the links to zend_parse_parameters and the others zend functions are ok but i can't work with php APIs. Why ? I think something is missing in config.m4 or in Makefile.in... could anybody help me? thx