Php/docs/migration55.new-features
新的特性
新增 Generators
Support for generators has been added via the yield keyword. Generators provide an easy way to implement simple iterators without the overhead or complexity of implementing a class that implements the Iterator interface.
A simple example that reimplements the range()
function as a generator (at least for positive step
values):
<?phpfunction xrange($start, $limit, $step = 1) { for ($i = $start; $i <= $limit; $i += $step) { yield $i; }}echo 'Single digit odd numbers: ';/* 注意保存在内存中的数组绝不会被创建或返回 */ foreach (xrange(1, 9, 2) as $number) { echo "$number ";}?>
以上例程会输出：
Single digit odd numbers: 1 3 5 7 9
新增 finally 关键字
try-catch blocks now support a
finally
block for code that should be run regardless of whether an exception has
been thrown or not.
foreach 现在支持 list()
foreach 控制结构现在支持通过 list() 构造将嵌套数组分离到单独的变量。例如：
<?php$array = [ [1, 2], [3, 4],];foreach ($array as list($a, $b)) { echo "A: $a; B: $b\n";}?>
以上例程会输出：
A: 1; B: 2 A: 3; B: 4
关于 foreach 更深入的文档可参考相关手册页面。
empty() 支持任意表达式
empty() 现在支持传入一个任意表达式，而不仅是一个变量。例如：
<?phpfunction always_false() { return false;}if (empty(always_false())) { echo 'This will be printed.';}if (empty(true)) { echo 'This will not be printed.';}?>
以上例程会输出：
This will be printed.
array and string literal dereferencing
Array and string literals can now be dereferenced directly to access individual elements and characters:
<?phpecho 'Array dereferencing: ';echo [1, 2, 3][0];echo "\n";echo 'String dereferencing: ';echo 'PHP'[0];echo "\n";?>
以上例程会输出：
Array dereferencing: 1 String dereferencing: P
新的密码哈希 API
A 新的密码哈希 API that makes it easier to securely hash and manage passwords using the same underlying library as crypt() in PHP has been added. See the documentation for password_hash() for more detail.
Apache 2.4 handler supported on Windows
The Apache 2.4 handler SAPI is now supported on Windows.
改进 GD
对 GD 扩展做了多方面的改进，包括：
- 翻转支持使用新的 imageflip() 函数。
- 高级裁剪支持使用 imagecrop() & imagecropauto() 函数。
- WebP 的读写分别支持使用 imagecreatefromwebp() & imagewebp() 。
