雙冒號操做符即做用域限定操做符Scope Resolution Operator能夠訪問靜態、const和類中重寫的屬性與方法。php
在類定義外使用的話，使用類名調用。在PHP 5.3.0，可使用變量代替類名。app
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<?php
class
Fruit {
const
CONST_VALUE =
'Fruit Color'
;
}
$classname
=
'Fruit'
;
echo
$classname
::CONST_VALUE;
// As of PHP 5.3.0
echo
Fruit::CONST_VALUE;
?>
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Program List：在類定義外部使用::ide
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<?php
class
Fruit {
const
CONST_VALUE =
'Fruit Color'
;
}
class
Apple
extends
Fruit
{
public
static
$color
=
'Red'
;
public
static
function
doubleColon() {
echo
parent::CONST_VALUE .
"\n"
;
echo
self::
$color
.
"\n"
;
}
}
Apple::doubleColon();
?>
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程序運行結果：ui
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Fruit Color Red
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Program List：調用parent方法this
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<?php
class
Fruit
{
protected
function
showColor() {
echo
"Fruit::showColor()\n"
;
}
}
class
Apple
extends
Fruit
{
// Override parent's definition
public
function
showColor()
{
// But still call the parent function
parent::showColor();
echo
"Apple::showColor()\n"
;
}
}
$apple
=
new
Apple();
$apple
->showColor();
?>
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程序運行結果：spa
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Fruit::showColor()
Apple::showColor()
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Program List：使用做用域限定符code
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<?php
class
Apple
{
public
function
showColor()
{
return
$this
->color;
}
}
class
Banana
{
public
$color
;
public
function
__construct()
{
$this
->color =
"Banana is yellow"
;
}
public
function
GetColor()
{
return
Apple::showColor();
}
}
$banana
=
new
Banana;
echo
$banana
->GetColor();
?>
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程序運行結果：ci
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Banana is yellow
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Program List：調用基類的方法作用域
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<?php
class
Fruit
{
static
function
color()
{
return
"color"
;
}
static
function
showColor()
{
echo
"show "
. self::color();
}
}
class
Apple
extends
Fruit
{
static
function
color()
{
return
"red"
;
}
}
Apple::showColor();
// output is "show color"!
?>
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程序運行結果：string
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show color
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