I created this topic and I answer to myself because this exerience seems interesting to share.
My machine is powered by a 64-bit processor, and executes PHP Apache LAMPP in 32-bit mode. The script, which until now has always worked in 64 bits, including at the host, no longer works.
So, take care! In my case, the offending line was:
for ($walkBit=0x80000000; !(($walkBit>>1) & $this->oTotInxCnt); $walkBit>>=1);
I simply replaced by:
for ($walkBit=0x40000000; !(($walkBit>>1) & $this->oTotInxCnt); $walkBit>>=1);
This "limitation" is not really annoying for me.