PHP wants to realize that a field cannot be modified after it is assigned a value. How to achieve this?

php itself does not have modifiers like C# readonly, it should be implemented through design

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php itself does not have modifiers like C# readonly, it should be implemented through design

Isn’t it enough to just use constants?
define(key,value)

Talk is cheap,i will show you the code demo.
Like this:

<code>//1.first snippet
class HelloSomeOne{
 const NAME = "PHP技术大全";
 //todo something else.
}
//2. second snippet
//not in class body inner
const NAME = "PHP技术大全";</code>

php does not provide such a function, but in object-oriented design, it can be achieved through the set/get method.

<code>class {
    private $a = null;
    
    public function setA($a) {
        if (null === $this->a) {
            $this->a = $a;
        }
    }

    public function getA() {
        return $this->a;
    }
}</code>

For the set/get method, you can use the two magic functions __set/__get to achieve better writing effect.

You can use define in PHP scripts, and you can use const in PHP classes