#! /usr/local/bin/php input: 4611686018427387903 binary: 0011111111111111111111111111111111111111111111111111111111111111 bindec(): 4611686018427387903 input: 4611686018427387904 binary: 0100000000000000000000000000000000000000000000000000000000000000 bindec(): 4611686018427387904 NOTE: See the rollover? Watch it next time around... input: 9223372036854775807 binary: 0111111111111111111111111111111111111111111111111111111111111111 bindec(): 9223372036854775807 NOTE: PHP_INT_MAX input: -9223372036854775808 binary: 1000000000000000000000000000000000000000000000000000000000000000 bindec(): 9223372036854775808 NOTE: interpreted to be one more than PHP_INT_MAX input: -1 binary: 1111111111111111111111111111111111111111111111111111111111111111 bindec(): 18446744073709551616 NOTE: interpreted to be the largest unsigned integer (18446744073709551615) but skewed by float precision