IT Services Circle

Jan 19, 2025 · Backend Development

Analysis of PHP Hexadecimal Addition Bug Caused by Lexer Change from Flex to re2c

An in‑depth examination of a long‑standing PHP bug where the expression 0x00+2 incorrectly evaluates to 4, tracing its origin to the switch from flex to re2c in the lexer of PHP 5.3, detailing affected versions, code behavior, and the eventual fix in PHP 5.3.11.