PHP强制转换为我的课程 [英] PHP Cast to my class

问题描述

为什么这不可能:

$user = (User) $u[0];

但这是可能的

$bool = (boolean) $res['success'];

我使用PHP 7.0.

I use PHP 7.0.

推荐答案

据我所知，在PHP中，您只能转换为某些类型:

As I know, in PHP you can only cast to some types:

(int), (integer) - cast to integer
(bool), (boolean) - cast to boolean
(float), (double), (real) - cast to float
(string) - cast to string
(binary) - cast to binary string (PHP 6)
(array) - cast to array
(object) - cast to object
(unset) - cast to NULL (PHP 5) (depracted in PHP 7.2) (removed in 8.0)

(请参见类型转换)

相反，您可以使用 instanceof 来检查特定类型:

Instead you could use instanceof to check of specific type:

if($yourvar instanceof YourClass) {
    //DO something
} else {
    throw new Exception('Var is not of type YourClass');
}

编辑

正如SzabolcsPáll在回答中所提到的，也可以声明返回类型或参数类型，但在这种情况下，如果类型不匹配，则会引发异常( TypeError )

As mentioned by Szabolcs Páll in his answer, it is also possible to declare a return type or parameter type, but in that cases an exception (TypeError) will be throwen, if the type does not match.

function test(): string
{
    return 'test';
}

function test(string $test){
    return "test" . $test;
}

自PHP 7.2起，还可以通过添加?使类型为空.在他们面前:

Since PHP 7.2 it is also possible to make the types nullable by adding ? in front of them:

function test(): ?string
{
    return null;
}

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