__set() Method

__set() is a magic method: it is called when writing data to inaccessible (protected or private) or non-existing properties. It is used to give a value to the property.

That way, it is possible to create dynamically properties, without hardcoding them.

The __set() method is usually paired with the __get() method.

The method signature is public function __set(string $name, mixed $value): void. The $name argument is the name of the property being interacted with. The $value argument specifies the value the $name-ed property should be set to. The return value of __set() is ignored because of the way PHP processes the assignment operator.

The method must be declared as public, or it is implicit. Arguments cannot be passed by reference. Property overloading only works in object context and will not be triggered in static context.

<?php

    class X {
        private $values = ['a' => 1,
                           'b' => 2,
                           ];

        // Checks the dictionary, or return 0
        function __set($name, $value) {
            if (isset($this->values[$name])) {
                $this->values[$name] = $value;
            }

            //do not set new values
        }
    }

?>

Documentation

See also PHP’s magic methods: Invoke, toString, get, set – Class wizardry in a nutshell.

Related : Magic Methods, __get() Method, __isset() Method, Magic Constants, __unset() Method, Magic Methods, Magic Property, Property Hook