New E_WARNING and E_NOTICE errors have been introduced when invalid strings are coerced using operators expecting numbers (+ - * / ** % << >> | & ^) or their assignment equivalents. An E_NOTICE is emitted when the string begins with a numeric value but contains trailing non-numeric characters, and an E_WARNING is emitted when the string does not contain a numeric value. &example.outputs; Previously, 3-octet octal string escape sequences would overflow silently. Now, they will still overflow, but E_WARNING will be emitted. &example.outputs; Whilst $this is considered a special variable in PHP, it lacked proper checks to ensure it wasn't used as a variable name or reassigned. This has now been rectified to ensure that $this cannot be a user-defined variable, reassigned to a different value, or be globalised. Session IDs will no longer be hashed upon generation. With this change brings about the removal of the following four ini settings: session.entropy_file session.entropy_length session.hash_function session.hash_bits_per_character And the addition of the following two ini settings: session.sid_length - defines the length of the session ID, defaulting to 32 characters for backwards compatibility) session.sid_bits_per_character - defines the number of bits to be stored per character (i.e. increases the range of characters that can be used in the session ID), defaulting to 4 for backwards compatibility precision If the value is set to -1, then the dtoa mode 0 is used. The default value is still 14. serialize_precision If the value is set to -1, then the dtoa mode 0 is used. The value -1 is now used by default. gd.jpeg_ignore_warning The default of this &php.ini; setting has been changed to 1, so by default libjpeg warnings are ignored. opcache.enable_cli The default of this &php.ini; setting has been changed to 1 (enabled) in PHP 7.1.2, and back to 0 (disabled) in PHP 7.1.7. Session IDs will now only be generated with a CSPRNG. TypeError exceptions for arg_info type checks will now provide more informative error messages. If the parameter type or return type accepts &null; (by either having a default value of &null; or being a nullable type), then the error message will now mention this with a message of "must be ... or null" or "must ... or be null."