Class Constants Visibility

Class constant may have a visibility option. This limits their accessibility to the current class, its class hierarchy or any other class. Visibilities for class constants are: private, protected and public.

<?php

class x {
    // This class can only be used in x
    private const C1 = 1;

    // This class can only be used in x and y
    protected const C2 = 1;

    // This class can be used in x, y and z
    private const C3 = 1;
}

class y extends x {
    // doSomething()
}

class z {
    // doSomething()
}

?>

Documentation

See also How to add visibility to 338 Class Constants in 25 seconds.

Related : Visibility

Added in PHP 7.1