Question

我读到对象（类的实例化）是全局范围的。这是有道理的，因为对象（同样，我不是在讨论类）应该很容易在代码的其他部分重用。但似乎这些信息是错误的。看看这个例子：

<?php

class test {
    public $returnvalue = "foobar";
}

$testobject = new test();


class getvalue {

    private $var;

    function printvalue() {
            $var = $testobject->returnvalue;
            print "$var";
    }

}

$getvalueobject = new getvalue();
$getvalueobject->printvalue();

?>

此代码返回错误：

尝试在...中获取非对象的属性

那么，在getvalue类中可以使$ testobject（类“test”的实例化）可用吗？

提前致谢。

Answer 1

<?php

class test {
    public $returnvalue = "foobar";
}

//$testobject = new test(); MOVE INTO METHOD


class getvalue {

    private $var;

    function printvalue() {
            $testobject = new test(); //For instance here
            $var = $testobject->returnvalue;
            print "$var";
    }

}

$getvalueobject = new getvalue();
$getvalueobject->printvalue();

?>

以下是文档：http://php.net/manual/en/language.variables.scope.php

Answer 2

<?php

class test {
    public $returnvalue = "foobar";
}

$testobject = new test();


class getvalue {

    public $classObject;

    function printvalue() {
        $var = $this->classObject->returnvalue;
        print "$var";
    }

}

$getvalueobject = new getvalue();
$getvalueobject->classObject = $testobject;
$getvalueobject->printvalue();

?>

类扩展的示例

<?php

class test {
    public $returnvalue = "foobar";
}

// If you use extends in PHP classes you can access all variables and methods from the base class (In this example the base class would be Test)
class getvalue extends test {
    function printvalue() {
        // Because we extended the base class Test, we can access it's public variable returnvalue
        $var = $this->returnvalue;
        print "$var";
    }

}

$getvalueobject = new getvalue();
$getvalueobject->printvalue();

?>

Answer 3

我错了。对象没有全局范围。

因此，如果你需要在另一个类中使用一个对象，那么你必须将它传递给__construct函数并将该对象存储在类属性中，或者你必须将它传递给使用它的函数：

<?php

class test {
    public $returnvalue = "foobar";
}

$testobject = new test();


class getvalue {

    private $var;
    private $testobject;

    function __construct($testobject) {
        $this->testobject = $testobject;
    }

    function printvalue() {
        $var = $this->testobject->returnvalue;
        print "$var";
    }

}

$getvalueobject = new getvalue($testobject);
$getvalueobject->printvalue();

?>

或

<?php

class test {
    public $returnvalue = "foobar";
}

$testobject = new test();


class getvalue {

    private $var;

    function printvalue($testobject) {
        $var = $testobject->returnvalue;
        print "$var";
    }

}

$getvalueobject = new getvalue();
$getvalueobject->printvalue($testobject);

?>

PHP对象（不是类）在另一个类中不可用

3 个答案: