Php/docs/migration72.incompatible
不向下兼容的变更
防止 number_format() 返回负零
之前版本中，number_format()
有可能会返回 -0。虽然这是符合 IEEE 754
规范的，但是这样会导致可读性不好，新版本中会将这样的负数去掉。
<?phpvar_dump(number_format(-0.01)); // 新版本输出 string(1) "0" 旧版本输出 string(2) "-0"
转换对象和数组中的数字键
将数组转换为对象，或将对象转换为数组时，数字键现在得到了更好的处理（无论是通过显式转换还是通过 settype() 函数）。
这意味着现在可以访问数组中的整数(或者说是字符串整数)键，这些键会映射到对象中：
<?php// array to object$arr = [0 => 1];$obj = (object)$arr;var_dump( $obj, $obj->{'0'}, // 新写法 $obj->{0} // 新写法);
以上例程会输出：
object(stdClass)#1 (1) {
["0"]=> // string key now, rather than integer key
int(1)
}
int(1)
int(1)
从对象转换成的数组中的整数（或者说是字符串整数）键现在也可以直接访问：
<?php// object to array$obj = new class { public function __construct() { $this->{0} = 1; }};$arr = (array)$obj;var_dump( $arr, $arr[0], // 新写法 $arr['0'] // 新写法);
以上例程会输出：
array(1) {
[0]=> // integer key now, rather than string key
int(1)
}
int(1)
int(1)
get_class() 函数不再接受 null 参数
之前版本中，传递 null 给 get_class()
函数将返回当前类名。在新版本中，此行为会抛出一个
E_WARNING 错误。如果想实现与之前版本同样的效果，请不要传递任何参数进来。
计算非可数类型（non-countable）时发出警告
对非可数类型调用 count()（或
sizeof()）函数，会抛出一个
E_WARNING 错误。
<?phpvar_dump( count(null), // NULL is not countable count(1), // integers are not countable count('abc'), // strings are not countable count(new stdclass), // objects not implementing the Countable interface are not countable count([1,2]) // arrays are countable);
以上例程会输出：
Warning: count(): Parameter must be an array or an object that implements Countable in %s on line %d Warning: count(): Parameter must be an array or an object that implements Countable in %s on line %d Warning: count(): Parameter must be an array or an object that implements Countable in %s on line %d Warning: count(): Parameter must be an array or an object that implements Countable in %s on line %d int(0) int(1) int(1) int(1) int(2)
ext/hash 从资源变成对象
As part of the long-term migration away from resources, the Hash extension has been updated to use objects instead of resources. The change should be seamless for PHP developers, except for where is_resource() checks have been made (which will need updating to is_object() instead).
SSL/TLS 的默认选项的改进
下列默认选项被修改：
-
tls://默认为 TLSv1.0 or TLSv1.1 or TLSv1.2 -
ssl://成为tls://的别名 -
STREAM_CRYPTO_METHOD_TLS_*常量默认为 TLSv1.0 或 TLSv1.1 + TLSv1.2，替代之前的 TLSv1.0
gettype() 在闭包资源中的返回值
之前版本中，如果在一个闭包资源中使用 gettype()
会返回字符串 "unknown type"，现在将会返回字符
"resource (closed)"。
is_object() 和 __PHP_Incomplete_Class
之前版本中，对 __PHP_Incomplete_Class
调用 is_object() 函数会返回
false，现在会返回 true。
Windows 支持
官方支持的最低 Windows 版本为 Windows 7/Server 2008 R2。
Checks on default property values of traits
Compatibility checks upon default trait property values will no longer perform casting.
object 保留字的变化
object 在之前的 PHP 7.0 版本
中被声明为软保留字（soft-reserved）。现在变更为强制保留字，禁止在任何类或接口中使用该名称。
NetWare 支持
NetWare 已不再被支持。
array_unique() with SORT_STRING
While array_unique() with SORT_STRING
formerly copied the array and removed non-unique elements (without packing
the array afterwards), now a new array is built by adding the
unique elements. This can result in different numeric indexes.
bcmod() changes with floats
The bcmod() function no longer truncates fractional
numbers to integers. As such, its behavior now follows
fmod(), rather than the % operator.
For example bcmod('4', '3.5') now returns
0.5 instead of 1.
Hashing functions and non-cryptographic hashes
The hash_hmac(), hash_hmac_file(),
hash_pbkdf2(), and hash_init() (with
HASH_HMAC) functions no longer accept non-cryptographic
hashes.
json_decode() 函数变更
The json_decode() function option,
JSON_OBJECT_AS_ARRAY, is now used if the second
parameter (assoc) is null. Previously,
JSON_OBJECT_AS_ARRAY was always ignored.
rand() and mt_rand() output
Sequences generated by rand() and mt_rand() for a specific seed may differ from PHP 7.1 on 64-bit machines (due to the fixing of a modulo bias bug in the implementation).
Changes to date_parse() and date_parse_from_format()
The zone element of the array returned by date_parse() and
date_parse_from_format() represents seconds instead of
minutes now, and its sign is inverted. For instance -120
is now 7200.
