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Difference: Once defined, const cannot be changed, while variables modified by static can be changed. const can only modify class attributes, not class methods; static can modify attributes as well as methods.
The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer
static and The difference between const variables
static variables
1.static static variables we can modify them , but we cannot modify const variables
2.static static variables can modify permissions
3.Similar to java, inside the class, satic The body of the modified method cannot access non-staic member variables of the class, but can only access the class's staic variables and the class's const constants
class staticTest1 { var $var1 = "hello"; public static $var2 = "hellostatic"; //public, protected, private const var3 = "helloconst"; public static function displayDifferent(){ ### echo $this->$var1."<br>";//不能访问普通变量 echo staticTest1::$var2."<br>";//可以访问类的静态变量 echo self::var3."<br>";//不能用$this::var3, self::var3代表当前类,$this::var3代表当前对象 } }
//You can call the method in two ways
//第一种,通过对象调用 $test1 = new staticTest1(); echo $test1->displayDifferent(); echo "<br>"; //第二种,通过类调用 echo staticTest1::displayDifferent(); echo "<br>";
By the way, "::" can only access static variables and methods for objects, and self can only use "::" to call members of the current class
1. Const variables can only modify member variables, not methods
2. No modification permission is required
3 .Because const variables belong to the entire class and do not belong to an object, they cannot be accessed through objects. For example, $this->constvariable does not allow
class constTest1 { var $var1 = "welcome"; // public const pi = 3.14;//不能加修饰权限 const pi = 3.14; // const function displayDifferent() {//function前不能加const // // } function displayDifferent() { echo self::pi."<br>"; // echo $this::pi."<br>"; } static function displayDifferent2() { echo self::pi."<br>"; // echo $this::pi."<br>"; //这句话不行。 } }
two method calls
//第一种,通过对象调用 $test2 = new constTest1(); echo $test2->displayDifferent(); //第二种,通过类调用 //echo constTest1::displayDifferent();//对象名用"::"只能访问静态变量和方法,所以这个不行 echo constTest1::displayDifferent2();
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