What is the difference between php constants and static variables

The difference between constants and static variables in php: 1. Constants are immutable quantities, while static variables can be assigned and changed through self; 2. In terms of compilation efficiency, the compilation process of constants is faster, while The compilation process for static variables is slower.

The operating environment of this tutorial: windows10 system, PHP7.1 version, DELL G3 computer

What is the difference between php constants and static variables

In terms of efficiency: the constant compilation process is much faster than static variables.

Code:

<?php
error_reporting(E_ALL);
class A {
 
    const c = 9;
    public static $b = 5;
 
    public function setst ($ca) {
        self::$b = $ca;
    }
}
 
$obj = new A;
echo $obj->c;//出错，是类的属性，不是对象的属性
echo $obj->$b;//出错，是类的属性，不是对象的属性
echo $obj::c;//ok，
echo A::c;//ok
echo $obj::$b;//ok
echo A::$b;//ok
$obj->setst(100);//更改静态变量的值
echo $obj::$b;//更改成功
 
?>

Conclusion:

Only the properties of the instance can be accessed using $obj->c.

Static variables and constants are attributes of a class. Class attributes are accessed using double colons (::), and can be accessed through object or class names.

Constants are immutable, and static variables can be assigned and changed through self.

const constants: immutable attributes of a class

static variables: variable attributes of a class

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