This problem exists in 3.0.3 and 3.0.5 and probably other versions. Sybase versions tested were 11.0.3 and ASE 11.5.1 running on AIX 4.3 and Digital Unix 4.0d.  PHP was running as an apache (1.3.3) module on AIX 4.3 on 64-bit hardware.

The following patch fixes the problem for me, but someone else probably needs to try it out to make sure I didn't break something else.

*** php3_sybase.h       Sun Oct  4 20:22:42 1998
--- php3_sybase.h.new   Wed Oct 21 11:43:37 1998
***************
*** 91,96 ****
--- 91,97 ----
  #define anyintcol(j) (coltype(j)==SYBINT4?intcol(j):(coltype(j)==SYBINT2?small
intcol(j):tinyintcol(j)))
  #define charcol(i) ((DBCHAR *) dbdata(sybase_ptr->link,i))
  #define floatcol(i) ((float) *(DBFLT8 *) dbdata(sybase_ptr->link,i))
+ #define realcol(i) ((float) *(DBREAL *) dbdata(sybase_ptr->link,i))

  typedef struct sybase_link_struct sybase_link;


*** sybase.c    Sun Oct  4 20:23:05 1998
--- sybase.c.new        Wed Oct 21 11:43:01 1998
***************
*** 626,634 ****
                        result->type = IS_STRING;
                        break;
                }
!               /*case SYBFLT8:*/
!               case SYBREAL: {
                        result->value.dval = (double) floatcol(offset);
                        result->type = IS_DOUBLE;
                        break;
                }
--- 626,637 ----
                        result->type = IS_STRING;
                        break;
                }
!               case SYBFLT8:
                        result->value.dval = (double) floatcol(offset);
+                       result->type = IS_DOUBLE;
+                       break;
+               case SYBREAL: {
+                       result->value.dval = (double) realcol(offset);
                        result->type = IS_DOUBLE;
                        break;
                }