Implementing dynamic getter and setter in PHP.

getter-sample.php

<?php

class ModelBase {
    static $attr_accessible = array();
    static $attr_readable = array();
    static $attr_writable = array();

    public function __get($attr) {
        $getter = "get_{$attr}";
        if (in_array($attr, static::$attr_accessible) || in_array($attr, static::$attr_readable)) {
            return $this->$attr;
        } else if (method_exists($this)) {
            return $this->$getter();
        } else {
            trigger_error("attribute '{$attr}' is not found.");
        }
    }

    public function __set($attr, $value) {
        $setter = "set_{$attr}";
        if (in_array($attr, static::$attr_accessible) || in_array($attr, static::$attr_writable)) {
            $this->$attr = $value;
        } else if (method_exists($this)) {
            $this->$setter($value);
        } else {
            trigger_error("attribute '{$attr}' is not found.");
        }
    }
}

Line 23: method_exists() expects 2 parameters