PHP 8.0 UPGRADE NOTES

1. Backward Incompatible Changes
2. New Features
3. Changes in SAPI modules
4. Deprecated Functionality
5. Changed Functions
6. New Functions
7. New Classes and Interfaces
8. Removed Extensions and SAPIs
9. Other Changes to Extensions
10. New Global Constants
11. Changes to INI File Handling
12. Windows Support
13. Other Changes
14. Performance Improvements


========================================
1. Backward Incompatible Changes
========================================

- Core:
 . Methods with the same name as the class are no longer interpreted as
 constructors. The __construct() method should be used instead.
 . Removed ability to call non-static methods statically.
 . Removed (unset) cast.
 . Removed track_errors ini directive. This means that $php_errormsg is no
 longer available. The error_get_last() function may be used instead.
 . Removed the ability to define case-insensitive constants. The third
 argument to define() may no longer be true.
 . Access to undefined constants now always results in an Error exception.
 Previously, unqualified constant accesses resulted in a warning and were
 interpreted as strings.
 . Removed ability to specify an autoloader using an __autoload() function.
 spl_autoload_register() should be used instead.
 . Removed the $errcontext argument for custom error handlers.
 . Removed create_function(). Anonymous functions may be used instead.
 . Removed each(). foreach or ArrayIterator should be used instead.
 . Removed ability to unbind $this from closures that were created from a
 method, using Closure::fromCallable() or ReflectionMethod::getClosure().
 . Also removed ability to unbind $this from proper closures that contain uses
 of $this.
 . Removed ability to use array_key_exists() with objects. Use one of isset()
 or property_exists() instead.
 . Any array that has a number n as its first numeric key will use n+1 for
 its next implicit key. Even if n is negative.
 RFC: https://wiki.php.net/rfc/negative_array_index
 . The default error_reporting level is now E_ALL. Previously it excluded
 E_NOTICE and E_DEPRECATED.
 . display_startup_errors is now enabled by default.
 . Using "parent" inside a class that has no parent will now result in a
 fatal compile-time error.
 . The @ operator will no longer silence fatal errors (E_ERROR, E_CORE_ERROR,
 E_COMPILE_ERROR, E_USER_ERROR, E_RECOVERABLE_ERROR, E_PARSE). Error handlers
 that expect error_reporting to be 0 when @ is used, should be adjusted to
 use a mask check instead:

 // Replace
 function my_error_handler($err_no, $err_msg, $filename, $linenum) {
 if (error_reporting() == 0) {
 return; // Silenced
 }
 // ...
 }

 // With
 function my_error_handler($err_no, $err_msg, $filename, $linenum) {
 if (!(error_reporting() & $err_no)) {
 return; // Silenced
 }
 // ...
 }

 Additionally, care should be taken that error messages are not displayed in
 production environments, which can result in information leaks. Please
 ensure that display_errors=Off is used in conjunction with error logging.
 . Inheritance errors due to incompatible method signatures (LSP violations)
 will now always generate a fatal error. Previously a warning was generated
 in some cases.
 RFC: https://wiki.php.net/rfc/lsp_errors
 . The precedence of the concatenation operator has changed relative to
 bitshifts and addition as well as subtraction.
 RFC: https://wiki.php.net/rfc/concatenation_precedence
 . Arguments with a default-value that resolves to null at run-time will no
 longer implicitly mark the argument type as nullable. Either use an explicit
 nullable type, or an explicit null default value instead.

 // Replace
 function test(int $arg = CONST_RESOLVING_TO_NULL) {}
 // With
 function test(?int $arg = CONST_RESOLVING_TO_NULL) {}
 // Or
 function test(int $arg = null) {}
 . A number of warnings have been converted into Error exceptions:

 * Attempting to write to a property of a non-object. Previously this
 implicitly created an stdClass object for null, false and empty strings.
 * Attempting to append an element to an array for which the PHP_INT_MAX key
 is already used.
 * Attempting to use an invalid type (array or object) as an array key or
 string offset.
 * Attempting to write to an array index of a scalar value.
 * Attempting to unpack a non-array/Traversable.

 A number of notices have been converted into warnings:

 * Attempting to read an undefined variable.
 * Attempting to read an undefined property.
 * Attempting to read a property of a non-object.
 * Attempting to access an array index of a non-array.
 * Attempting to convert an array to string.
 * Attempting to use a resource as an array key.
 * Attempting to use null, a boolean or a float as a string offset.
 * Attempting to read an out-of-bounds string offset.

 RFC: https://wiki.php.net/rfc/engine_warnings
 . Unexpected characters in source files (such as null bytes outside of
 strings) will now result in a ParseError exception instead of a compile
 warning.
 . Uncaught exceptions now go through "clean shutdown", which means that
 destructors will be called after an uncaught exception.

- COM:
 . Removed the ability to import case-insensitive constants from type
 libraries. The second argument to com_load_typelib() may no longer be false;
 com.autoregister_casesensitive may no longer be disabled; case-insensitive
 markers in com.typelib_file are ignored.

- Date:
 . mktime() and gmmktime() now require at least one argument. time() can be
 used to get the current timestamp.

- dom:
 . Remove unimplemented classes from ext/dom that had no behavior and contained
 test data. These classes have also been removed in the latest version of DOM
	standard:

 * DOMNameList
 * DomImplementationList
 * DOMConfiguration
 * DomError
 * DomErrorHandler
 * DOMImplementationSource
 * DOMLocator
 * DOMUserDataHandler
 * DOMTypeInfo

- Exif:
 . Removed read_exif_data(). exif_read_data() should be used instead.

- Filter:
 . The FILTER_FLAG_SCHEME_REQUIRED and FILTER_FLAG_HOST_REQUIRED flags for the
 FILTER_VALIDATE_URL filter have been removed. The scheme and host are (and
 have been) always required.
 . The INPUT_REQUEST and INPUT_SESSION source for filter_input() etc have been
 removed. These were never implemented and their use always generated a
 warning.

- GD:
 . The GD extension now uses objects as the underlying data structure for
 images, rather than resources. These objects are completely opaque, i.e.
 they don't have any methods.
 . The deprecated function image2wbmp() has been removed.
 RFC: https://wiki.php.net/rfc/image2wbmp
 . The deprecated functions png2wbmp() and jpeg2wbmp() have been removed.
 RFC: https://wiki.php.net/rfc/deprecate-png-jpeg-2wbmp
 . The default $mode parameter of imagecropauto() no longer accepts -1.
 IMG_CROP_DEFAULT should be used instead.

- GMP:
 . gmp_random() has been removed. One of gmp_random_range() or
 gmp_random_bits() should be used instead.

- Intl:
 . The deprecated constant INTL_IDNA_VARIANT_2003 has been removed.
 RFC: https://wiki.php.net/rfc/deprecate-and-remove-intl_idna_variant_2003
 . The deprecated Normalizer::NONE constant has been removed.

- LDAP:
 . The deprecated function ldap_sort has been removed.

- Mbstring:
 . The mbstring.func_overload directive has been removed. The related
 MB_OVERLOAD_MAIL, MB_OVERLOAD_STRING, and MB_OVERLOAD_REGEX constants have
 also been removed. Finally, the "func_overload" and "func_overload_list"
 entries in mb_get_info() have been removed.
 . mb_parse_str() can no longer be used without specifying a result array.
 . A number of deprecated mbregex aliases have been removed. See the following
 list for which functions should be used instead:

 * mbregex_encoding() -> mb_regex_encoding()
 * mbereg() -> mb_ereg()
 * mberegi() -> mb_eregi()
 * mbereg_replace() -> mb_ereg_replace()
 * mberegi_replace() -> mb_eregi_replace()
 * mbsplit() -> mb_split()
 * mbereg_match() -> mb_ereg_match()
 * mbereg_search() -> mb_ereg_search()
 * mbereg_search_pos() -> mb_ereg_search_pos()
 * mbereg_search_regs() -> mb_ereg_search_regs()
 * mbereg_search_init() -> mb_ereg_search_init()
 * mbereg_search_getregs() -> mb_ereg_search_getregs()
 * mbereg_search_getpos() -> mb_ereg_search_getpos()
 * mbereg_search_setpos() -> mb_ereg_search_setpos()

 . The 'e' modifier for mb_ereg_replace() has been removed.
 mb_ereg_replace_callback() should be used instead.
 . A non-string pattern argument to mb_ereg_replace() will now be interpreted
 as a string instead of an ASCII codepoint. The previous behavior may be
 restored with an explicit call to chr().
 . The $is_hex parameter, which was not used internally, has been removed from
 mb_decode_numericentity().
 . The legacy behaviour of passing the encoding as the third argument instead of an offset for the mb_strrpos
 function has been removed, provide an explicit 0 offset with the encoding as the fourth argument.

- PCRE:
 . When passing invalid escape sequences they are no longer interpreted as
 literals. This behaviour previously required the X modifier - which is
 now ignored.

- PDO:
 . The method PDOStatement::setFetchMode() now accepts the following signature:

 PDOStatement::setFetchMode($mode, $classname, $params)

- PDO_ODBC:
 . The php.ini directive pdo_odbc.db2_instance_name has been removed

- Reflection:
 . The method signatures

 ReflectionClass::newInstance($args)
 ReflectionFunction::invoke($args)
 ReflectionMethod::invoke($object, $args)

 have been changed to:

 ReflectionClass::newInstance(...$args)
 ReflectionFunction::invoke(...$args)
 ReflectionMethod::invoke($object, ...$args)

 Code that must be compatible with both PHP 7 and PHP 8 can use the following
 signatures to be compatible with both versions:

 ReflectionClass::newInstance($arg = null, ...$args)
 ReflectionFunction::invoke($arg = null, ...$args)
 ReflectionMethod::invoke($object, $arg = null, ...$args)

 . The ReflectionType::__toString() method will now return a complete debug
 representation of the type, and is no longer deprecated. In particular the
 result will include a nullability indicator for nullable types. The format
 of the return value is not stable and may change between PHP versions.

- Socket:
 . The deprecated AI_IDN_ALLOW_UNASSIGNED and AI_IDN_USE_STD3_ASCII_RULES
 flags for socket_addrinfo_lookup() have been removed.

- SPL:
 . SplFileObject::fgetss() has been removed.
 . SplHeap::compare($a, $b) now specifies a method signature. Inheriting
 classes implementing this method will now have to use a compatible
 method signature.

- Standard:
 . assert() will no longer evaluate string arguments, instead they will be
 treated like any other argument. assert($a == $b) should be used instead of
 assert('$a == $b'). The assert.quiet_eval ini directive and
 ASSERT_QUIET_EVAL constants have also been removed, as they would no longer
 have any effect.
 . parse_str() can no longer be used without specifying a result array.
 . fgetss() has been removed.
 . The string.strip_tags filter has been removed.
 . The needle argument of strpos(), strrpos(), stripos(), strripos(), strstr(),
 strchr(), strrchr(), and stristr() will now always be interpreted as a
 string. Previously non-string needles were interpreted as an ASCII code
 point. An explicit call to chr() can be used to restore the previous
 behavior.
 . The needle argument for strpos(), strrpos(), stripos(), strripos(), strstr() and stristr() can now be empty.
 . The length argument for substr(), substr_count(), substr_compare(), and
 iconv_substr() can now be null. Null values will behave as if no length
 argument was provided and will therefore return the remainder of the string
 instead of an empty string.
 . The length argument for array_splice() can now be null. Null values will
 behave identically to omitting the argument, thus removing everything from
 the 'offset' to the end of the array.
 . The 'salt' option of password_hash() is no longer supported. If the 'salt'
 option is used a warning is generated, the provided salt is ignored, and a
 generated salt is used instead.
 . The quotemeta() function will now return an empty string if an empty string
 was passed. Previously false was returned.
 . hebrevc() has been removed.
 . convert_cyr_string() has been removed.
 . money_format() has been removed.
 . ezmlm_hash() has been removed.
 . get_magic_quotes_gpc() and get_magic_quotes_gpc_runtime() has been removed.
 . FILTER_SANITIZE_MAGIC_QUOTES has been removed.
 . Calling implode() with parameters in a reverse order ($pieces, $glue) is no
 longer supported.

- tidy:
 . The $use_include_path parameter, which was not used internally, has been
 removed from tidy_repair_string().

- XML:
 . xml_parser_create(_ns) will now return an XmlParser object rather than a
 resource. Return value checks using is_resource() should be replaced with
 checks for `false`. The xml_parser_free() function no longer has an effect,
 instead the XmlParser instance is automatically destroyed if it is no longer
 referenced.

- XMLWriter:
 . The XMLWriter functions now accept and return, respectively, XMLWriter
 objects instead of resources.

- Zip:
 . The remove_path option of ZipArchive::addGlob() and ::addPattern() is now
 treated as arbitrary string prefix (for consistency with the add_path
 option), whereas formerly it was treated as directory name. This means that
 if no trailing directory separator is given, the following character is
 no longer stripped from the filename.

- Zlib:
 . gzgetss() has been removed.

========================================
2. New Features
========================================

- Core:
 . Added support for union types.
 RFC: https://wiki.php.net/rfc/union_types_v2
 . Added ValueError class.

========================================
3. Changes in SAPI modules
========================================

========================================
4. Deprecated Functionality
========================================

========================================
5. Changed Functions
========================================

========================================
6. New Functions
========================================

- SQLite3:
 . Add SQLite3::setAuthorizer() and respective class constants to set a
 userland callback that will be used to authorize or not an action on the
 database.
 PR: https://github.com/php/php-src/pull/4797

- Standard:
 . Added fdiv() method, which performs a floating-point division under
 IEEE 754 semantics. Division by zero is considered well-defined and
 will return one of Inf, -Inf or NaN.

========================================
7. New Classes and Interfaces
========================================

========================================
8. Removed Extensions and SAPIs
========================================

========================================
9. Other Changes to Extensions
========================================

- GD:
 . The $num_points parameter of imagepolygon(), imageopenpolygon() and
 imagefilledpolygon() is now optional, i.e. these functions may be called
 with either 3 or 4 arguments. If the arguments is omitted, it is calculated
 as count($points)/2.

========================================
10. New Global Constants
========================================

========================================
11. Changes to INI File Handling
========================================

========================================
12. Windows Support
========================================

========================================
13. Other Changes
========================================

========================================
14. Performance Improvements
========================================

- array_slice() on an array without gaps will no longer scan the whole array to find
 the start offset. This may significantly reduce the runtime of the function
 with large offsets and small lengths.