Notices and warnings on arithmetic with invalid strings

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.

<?php
'1b' + 'something';

The above example will output:

Notice: A non well formed numeric value encountered in %s on line %d
Warning: A non-numeric value encountered in %s on line %d

Warn on octal escape sequence overflow

Previously, 3-octet octal string escape sequences would overflow silently. Now, they will still overflow, but E_WARNING will be emitted.

<?php
var_dump("\500");

The above example will output:

Warning: Octal escape sequence overflow \500 is greater than \377 in %s on line %d
string(1) "@"

Inconsistency fixes to `$this`

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 ID generation without hashing

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

Changes to INI file handling

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 ID generation with a CSPRNG only

Session IDs will now only be generated with a CSPRNG.

More informative TypeError messages when `null` is allowed

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."

Other changes