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PHP 5.5.x#

1. 新特性#

1.1. 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):

<?php
function 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 

1.2. 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。

1.3. 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:

<?php
function 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.

1.4. array and string literal dereferencing#

Array and string literals can now be dereferenced directly to access individual elements and characters:

<?php
echo '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

1.5. 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.

1.6. 改进 GD#

对 GD 扩展做了多方面的改进,包括:


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