php7发布已有半月，最近有时间了解一下php7的新特性，当然，这个版本最大的特点是性能的提升。在下并非高手，欢迎大家指出错误，同时期待共同交流
1.在use语句增加了group支持
use FooLibrary\Bar\Baz\{ ClassA, ClassB, ClassC, ClassD as Fizbo };
2.增加??操作符
isset($_GET['mykey']) ? $_GET['mykey'] : ""笨重
$_GET['mykey'] ?: "" 当mykey不存在时会报一个E_NOTICE
$_GET['mykey'] ?? 'defaultvalue' 安全不会报E_NOTICE
$username = $_GET['user'] ?? 'nobody';
3. 64位PHP7字符串长度可以超过2^31次方字节。
4.增加Closure::call支持
Closure::call将一个闭包函数动态绑定到一个新的对象实例并调用执行该函数，
<span> 1</span> <?<span>php
</span><span> 2</span> <span>class</span><span> Value {
</span><span> 3</span> <span>protected</span> <span>$value</span><span>;
</span><span> 4</span>
<span> 5</span> <span>public</span> <span>function</span> __construct(<span>$value</span><span>) {
</span><span> 6</span> <span>$this</span>->value = <span>$value</span><span>;
</span><span> 7</span> <span>}
</span><span> 8</span>
<span> 9</span> <span>public</span> <span>function</span><span> getValue() {
</span><span>10</span> <span>return</span> <span>$this</span>-><span>value;
</span><span>11</span> <span>}
</span><span>12</span> <span>}
</span><span>13</span>
<span>14</span> <span>$three</span> = <span>new</span> Value(3<span>);
</span><span>15</span> <span>$four</span> = <span>new</span> Value(4<span>);
</span><span>16</span>
<span>17</span> <span>$closure</span> = <span>function</span> (<span>$delta</span>) { <span>var_dump</span>(<span>$this</span>->getValue() + <span>$delta</span><span>); };
</span><span>18</span> <span>$closure</span>->call(<span>$three</span>, 4<span>);
</span><span>19</span> <span>$closure</span>->call(<span>$four</span>, 4<span>);
</span><span>20</span> ?>
<span>21</span> <span>//</span><span> outputs int(7),int(8)</span>5.双引号字符串和heredocs里面支持使用\u{xxxxx}来声明unicode字符。
6.define对数组的支持
<span>1</span> <span>define</span>('ANIMALS', <span>array</span><span>(
</span><span>2</span> 'dog',
<span>3</span> 'cat',
<span>4</span> 'bird'
<span>5</span> <span>));
</span><span>6</span> <span>echo</span> ANIMALS[1]; <span>//</span><span> outputs "cat"</span>
7.增加比较运算符<=>
$a <=> $b
如果a等于b则为0
如果a大于b则为1
如果a小于b则为-1
8.php全局保留字可以声明使用
<span>1</span> <span>class</span><span> View {
</span><span>2</span> <span>public</span> <span>function</span> <span>include</span>(View <span>$view</span><span>) {
</span><span>3</span> <span>//</span><span>...</span>
<span>4</span> <span> }
</span><span>5</span> }include关键字可以当普通字符串关键字一样被使用
9.标量类型（int,float,string,bool）支持
增加declare(strict_types=1)指令声明是否严格类型校验，
当在文件头声明declare(strict_types=1)
<span>1</span> <<span>php
</span><span>2</span>
<span>3</span> <span>declare</span>(strict_types=1<span>);
</span><span>4</span> <span>function</span> add(<span>float</span> <span>$a</span>, <span>float</span> <span>$b</span>): <span>float</span><span> {
</span><span>5</span> <span>return</span> <span>$a</span> + <span>$b</span><span>;
</span><span>6</span> <span>}
</span><span>7</span> add(1, 2); <span>//</span><span> float(3)</span>以上代码如果不开启declare(strict_types=1)或许declare(strict_types=0)，php将自动转换参数和返回值到指定类型，
开启declare(strict_types=1)，如果参数类型不是flaot或许返回类型不是float则抛出错误
10.增加接口为用户层提供安全方便的随机数生成器。RFC: https://wiki.php.net/rfc/easy_userland_csprng (后续再议)
11.增加了yield from 操作符。https://wiki.php.net/rfc/generator-delegation (后续再议)
