__set() Method

__set() is a magic method : it is called when a property cannot be access, either because it doesn’t exist, or because its visibility prevents it. 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.

<?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

Related : Magic Methods, __get() Method, __isset() Method, Magic Constants