PHP. Руководство по PHP. 2005
gmp_clrbit
gmp_clrbit
Description
void gmp_clrbit (resource &a, int index)Clears (sets to 0) bit index in a. The index starts at 0.
Замечание: Unlike most of the other GMP functions, gmp_clrbit() must be called with a GMP resource that already exists (using gmp_init() for example). One will not be automatically created.