在使用PHP类时，我注意到在类中，当我以$this->variablename方式将函数中的变量定义为该类的属性时，它会自动成为该类的公共变量。
class example {
public function setstring() {
$this->string = "string";
}
}
那样
$class = new example();
echo $class->string;
输出：string
但是，如果我想创建只能访问类中函数的私有变量，那么无论如何只能在setstring()函数内部声明它们吗？而不是像这样在函数之外将它们声明为私有。
class example {
private $string ='';
public function setstring() {
$this->string = "string";
}
}
有人可能会这样做的原因是为了整洁，以免在课程开始时声明一长串私有变量。
答案 0 :(得分：6)
否，没有办法做到这一点。
在PHP中，您通常使用自记录注释按字母顺序在函数上方声明所有您的类/实例属性。这是最好的＆＃34;整洁＆＃34;并且清楚地写课程。还建议您根据需要使用getter和setter完全避免使用公共属性。
PHP的规范编码样式在PSR-1和PSR-2中定义。我还建议您查看PHPDoc。
请记住，在类方法范围内声明的变量将是该方法的私有变量。如果您打算从其他方法访问它，则只需要一个类属性。
<?php
class Example {
/**
* Holds a private string
* @var string
*/
private $string = '';
/**
* Sets the private string variable
*/
public function setString() {
$this->string = 'This string is accessible by other methods';
$privateVar = 'This string is only accessible from within this method';
}
}
答案 1 :(得分：1)
这不是一种语言功能，但是有一个非常简单有效的技巧：
class Test
{
/**
* Hidden dynamic data.
* @var object
*/
private $_ = (object)[];
public function setString()
{
$this->_->string = "string";
}
}
您可以将$_更改为所需的内容，但对我来说，它看起来确实比较笨拙。 $this->this也是一个选项。
答案 2 :(得分：0)
如何使用OOP在PHP类中创建私有变量 （面向对象编程）。
在PHP类中声明私有变量的最佳方法是在__Construction方法上方创建它们，按照惯例，您可以在美元符号（即$ _private_variable）后用下划线开头该变量，以让其他程序员阅读您的代码看到它是一个私有变量 brilliant ！
请在您的类中将所有变量声明为私有变量，但__getter和__setter始终为公共变量，除非您有理由不这样做。
使用__setter（__set）函数将值设置为类中的私有变量，然后在需要该值时，使用__getter（__get）函数返回值。
为了理解这一点，让我们创建一个很小的类，该类可以用于创建不同类型的Vehicle，这将使您了解如何正确创建私有变量，为其设置值并从中返回值准备好了吗？
<?php
Class Vehicle{
/* Delcaration of private variables */
private $_name = "Default Vehicle";
private $_model;
private $_type;
private $_identification;
/* Declaration of private arrays */
private $_mode = array();
private $feature = array();
/* Magic code entry function, think of it as a main() in C/C++ */
public function __construct( $name, $model, $type ){
$this->create_vehicle( $name, $model, $type );
}
/* __getter function */
public function __get( $variable ){
if( !empty($this->$variable) ){
$get_variable = $this->$variable;
}
return $get_variable;
}
/* __setter function */
public function __set( $variable, $target ){
$this->$variable = $target;
}
/* Private function */
private function create_vehicle( $name, $model, $type ){
$this->__set( "_name", $name );
$this->__set( "_model", $model);
$this->__set( "_type", $type );
}
}
//end of the class.
?>
<?php
/* Using the Vehicle class to create a vehicle by passing
three parameters 'vehicle name', 'vehicle model', 'vehicle type'
to the class.
*/
$toyota = new Vehicle("Toyotal 101", "TY101", "Sedan");
/* Get the name and store it in a variable for later use */
$vehicle_name = $toyota->__get('_name');
/* Set the vehicle mode or status */
$vehicle_mode = array(
'gas' => 50,
'ignition' => 'OFF',
'tire' => "OK",
'year' => 2020,
'mfg' => 'Toyoda',
'condition' => 'New'
);
/* Create vehicle features */
$vehicle_feature = array(
"Tire" => 4,
"Horse Power" => "V6",
"blah blah" => "foo",
"Airbag" => 2,
"Transmission" => "Automatic"
//....
);
/* Create vehicle identification */
$vehicle_identification = array(
"VIN" => "0001234567ABCD89",
"NAME" => $vehicle_name,
"FEATURE" => $vehicle_feature,
"MODEL" => $vehicle_mode,
"YEAR" => 2020,
"MFG" => "Totota"
);
/* Set vehicle identification */
$toyota->__set("_identification", $vehicle_identification );
/* Set vehicle features */
$toyota->__set("_feature", $vehicle_feature );
/* Set vehicle mode */
$toyota->__set("_mode", $vehicle_mode);
/* Retrieve information and store them in variable using __get (getter) */
$vehicle_name = $toyota->__get('_name');
$vehicle_mode = $toyota->__get('_mode');
$vehicle_id = $toyota->__get('_identification');
$vehicle_features = $toyota->__get('_feature');
$vehicle_type = $toyota->__get('_type');
$vehicle_model = $toyota->__get('_model');
/* Printing information using store values in the variables. */
echo "Printing Vehicle Information\n";
echo "*****************************\n";
echo "Vehicle name is $vehicle_name \n";
echo "Vehicle Model is $vehicle_model \n";
echo "Vehich type is $vehicle_type \n";
printf("\n\n");
echo "Printing Vehicle Mode\n";
echo "***********************\n";
print_r( $vehicle_mode );
printf("\n\n");
echo "Printing Vehicle Features\n";
echo "**************************\n";
print_r( $vehicle_features );
printf("\n\n");
echo "Printing Vehicle Identification\n";
echo "******************************\n";
print_r( $vehicle_id );
printf("\n\n");
?>
此代码的输出：
Printing Vehicle Information
*****************************
Vehicle name is Toyotal 101
Vehicle Model is TY101
Vehich type is Sedan
Printing Vehicle Mode
***********************
Array
(
[gas] => 50
[ignition] => OFF
[tire] => OK
[year] => 2020
[mfg] => Toyoda
[condition] => New
)
Printing Vehicle Features
**************************
Array
(
[Tire] => 4
[Horse Power] => V6
[blah blah] => foo
[Airbag] => 2
[Transmission] => Automatic
)
Printing Vehicle Identification
******************************
Array
(
[VIN] => 0001234567ABCD89
[NAME] => Toyotal 101
[FEATURE] => Array
(
[Tire] => 4
[Horse Power] => V6
[blah blah] => foo
[Airbag] => 2
[Transmission] => Automatic
)
[MODEL] => Array
(
[gas] => 50
[ignition] => OFF
[tire] => OK
[year] => 2020
[mfg] => Toyoda
[condition] => New
)
[YEAR] => 2020
[MFG] => Totota
)
要对此代码进行实时测试或实验，请参见demo，更名，并根据需要创建新的车辆。
我希望这会有所帮助。