参见英文答案 >
Predefined types of variable parameters4个
我在 https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Console/Output/Output.php第40行看到了这个代码,他们正在使用？int.
我在 https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Console/Output/Output.php第40行看到了这个代码,他们正在使用？int.
public function __construct(?int $verbosity = self::VERBOSITY_norMAL,bool $decorated = false,OutputFormatterInterface $formatter = null)
{
$this->verbosity = null === $verbosity ? self::VERBOSITY_norMAL : $verbosity;
$this->formatter = $formatter ?: new OutputFormatter();
$this->formatter->setDecorated($decorated);
}
它被称为Nullable类型.
将int定义为int或null.
Type declarations for parameters and return values can Now be marked as nullable by prefixing the type name with a question mark. This signifies that as well as the specified type,NULL can be passed as an argument,or returned as a value,respectively.
示例：
function nullOrInt(?int $arg){
var_dump($arg);
}
nullOrInt(100);
nullOrInt(null);
function nullOrInt将同时接受null和int.
参考：http://php.net/manual/en/migration71.new-features.php