当传递参数过少时将抛出错误

在过去如果我们调用一个用户定义的函数时，提供的参数不足，那么将会产生一个警告(warning)。 现在，这个警告被提升为一个错误异常(Error exception)。这个变更仅对用户定义的函数生效， 并不包含内置函数。例如：

Fatal error: Uncaught ArgumentCountError: Too few arguments to function test(), 0 passed in %s on line %d and exactly 1 expected in %s:%d

Forbid dynamic calls to scope introspection functions

Dynamic calls for certain functions have been forbidden (in the form of $func() or array_map('extract', ...), etc). These functions either inspect or modify another scope, and present with them ambiguous and unreliable behavior. The functions are as follows:

• assert() - with a string as the first argument
• compact()
• extract()
• func_get_args()
• func_get_arg()
• func_num_args()
• get_defined_vars()
• mb_parse_str() - with one arg
• parse_str() - with one arg

Warning: Cannot call func_num_args() dynamically in %s on line %d

Invalid class, interface, and trait names

The following names cannot be used to name classes, interfaces, or traits:

• void
• iterable

Numerical string conversions now respect scientific notation

Integer operations and conversions on numerical strings now respect scientific notation. This also includes the (int) cast operation, and the following functions: intval() (where the base is 10), settype(), decbin(), decoct(), and dechex().

Fixes to mt_rand() algorithm

mt_rand() will now default to using the fixed version of the Mersenne Twister algorithm. If deterministic output from mt_srand() was relied upon, then the MT_RAND_PHP with the ability to preserve the old (incorrect) implementation via an additional optional second parameter to mt_srand().

rand() aliased to mt_rand() and srand() aliased to mt_srand()

rand() and srand() have now been made aliases to mt_rand() and mt_srand(), respectively. This means that the output for the following functions have changed: rand(), shuffle(), str_shuffle(), and array_rand().

Disallow the ASCII delete control character in identifiers

The ASCII delete control character (0x7F) can no longer be used in identifiers that are not quoted.

error_log changes with syslog value

If the error_log ini setting is set to syslog, the PHP error levels are mapped to the syslog error levels. This brings finer differentiation in the error logs in contrary to the previous approach where all the errors are logged with the notice level only.

在不完整的对象上不再调用析构方法

对于在执行构造方法时抛出异常的对象，现在析构方法绝不会被调用。在先前的版本中，这个行为取决于对象是否在构造方法以外的地方呗引用（例如一个错误堆栈回溯）

call_user_func()不再支持对传址的函数的调用

call_user_func() 现在在调用一个以引用作为参数的函数时将始终产生一个警告。先前这取决于这个调用行为是否完全符合条件。

此外， call_user_func() 和 call_user_func_array() 在这种情况下将不再中断函数调用。现在会出现一个包含"expected reference"的警告信息，但函数调用将正常进行。

字符串不再支持空索引操作符

对字符串使用一个空索引操作符（例如$str[] = $x）将会抛出一个致命错误， 而不是静默地将其转为一个数组。

ini配置项移除

下列ini配置项已经被移除：

• session.entropy_file
• session.entropy_length
• session.hash_function
• session.hash_bits_per_character

Array ordering when elements are automatically created during by reference assignments has changed

The order of the elements in an array has changed when those elements have been automatically created by referencing them in a by reference assignment. For example:

array(2) {
  ["a"]=>
  &int(1)
  ["b"]=>
  &int(1)
}

array(2) {
  ["b"]=>
  &int(1)
  ["a"]=>
  &int(1)
}

Sort order of equal elements

The internal sorting algorithm has been improved, what may result in different sort order of elements, which compare as equal, than before.

Note:

Don't rely on the order of elements which compare as equal; it might change anytime.

Error message for E_RECOVERABLE errors

The error message for E_RECOVERABLE errors has been changed from "Catchable fatal error" to "Recoverable fatal error".

$options parameter of unserialize()

The allowed_classes element of the $options parameter of unserialize() is now strictly typed, i.e. if anything other than an array or a bool is given, unserialize() returns false and issues an E_WARNING.

DateTime constructor incorporates microseconds

DateTime and DateTimeImmutable now properly incorporate microseconds when constructed from the current time, either explicitly or with a relative string (e.g. "first day of next month"). This means that naive comparisons of two newly created instances will now more likely return false instead of true:

Fatal errors to Error exceptions conversions

In the Date extension, invalid serialization data for DateTime or DatePeriod classes, or timezone initialization failure from serialized data, will now throw an Error exception from the __wakeup() or __set_state() methods, instead of resulting in a fatal error.

In the DBA extension, data modification functions (such as dba_insert()) will now throw an Error exception instead of triggering a catchable fatal error if the key does not contain exactly two elements.

In the DOM extension, invalid schema or RelaxNG validation contexts will now throw an Error exception instead of resulting in a fatal error. Similarly, attempting to register a node class that does not extend the appropriate base class, or attempting to read an invalid property or write to a readonly property, will also now throw an Error exception.

In the IMAP extension, email addresses longer than 16385 bytes will throw an Error exception instead of resulting in a fatal error.

In the Intl extension, failing to call the parent constructor in a class extending Collator before invoking the parent methods will now throw an Error instead of resulting in a recoverable fatal error. Also, cloning a Transliterator object will now throw an Error exception on failure to clone the internal transliterator instead of resulting in a fatal error.

In the LDAP extension, providing an unknown modification type to ldap_batch_modify() will now throw an Error exception instead of resulting in a fatal error.

In the mbstring extension, the mb_ereg() and mb_eregi() functions will now throw a ParseError exception if an invalid PHP expression is provided and the 'e' option is used.

In the Mcrypt extension, the mcrypt_encrypt() and mcrypt_decrypt() will now throw an Error exception instead of resulting in a fatal error if mcrypt cannot be initialized.

In the mysqli extension, attempting to read an invalid property or write to a readonly property will now throw an Error exception instead of resulting in a fatal error.

In the Reflection extension, failing to retrieve a reflection object or retrieve an object property will now throw an Error exception instead of resulting in a fatal error.

In the Session extension, custom session handlers that do not return strings for session IDs will now throw an Error exception instead of resulting in a fatal error when a function is called that must generate a session ID.

In the SimpleXML extension, creating an unnamed or duplicate attribute will now throw an Error exception instead of resulting in a fatal error.

In the SPL extension, attempting to clone an SplDirectory object will now throw an Error exception instead of resulting in a fatal error. Similarly, calling ArrayIterator::append() when iterating over an object will also now throw an Error exception.

In the standard extension, the assert() function, when provided with a string argument as its first parameter, will now throw a ParseError exception instead of resulting in a catchable fatal error if the PHP code is invalid. Similarly, calling forward_static_call() outside of a class scope will now throw an Error exception.

In the Tidy extension, creating a tidyNode manually will now throw an Error exception instead of resulting in a fatal error.

In the WDDX extension, a circular reference when serializing will now throw an Error exception instead of resulting in a fatal error.

In the XML-RPC extension, a circular reference when serializing will now throw an instance of Error exception instead of resulting in a fatal error.

In the Zip extension, the ZipArchive::addGlob() method will now throw an Error exception instead of resulting in a fatal error if glob support is not available.

Lexically bound variables cannot reuse names

Variables bound to a closure via the use construct cannot use the same name as any superglobals, $this, or any parameter. For example, all of these function definition will result in a fatal error:

long2ip() parameter type change

long2ip() now expects an int instead of a string.

JSON encoding and decoding

The serialize_precision ini setting now controls the serialization precision when encoding doubles.

Decoding an empty key now results in an empty property name, rather than _empty_ as a property name.

object(stdClass)#1 (1) {
  [""]=>
  int(1)
}

When supplying the JSON_UNESCAPED_UNICODE flag to json_encode(), the sequences U+2028 and U+2029 are now escaped.

Changes to mb_ereg() and mb_eregi() parameter semantics

The third parameter to the mb_ereg() and mb_eregi() functions (regs) will now be set to an empty array if nothing was matched. Formerly, the parameter would not have been modified.

Drop support for the sslv2 stream

The sslv2 stream has now been dropped in OpenSSL.

Forbid "return;" for typed returns already at compile-time

Return statements without argument in functions which declare a return type now trigger E_COMPILE_ERROR (unless the return type is declared as void), even if the return statement would never be reached.