InputGetter.php

<?php
class InputGetter{
	function __get($key){
		return null;
	}
	
	function __construct($array){
		foreach($array as $key => $val){
			$this->$key = $val;
		}
	}
	
	function get($key, $default = null){
		return property_exists($this, $key) ? $this->$key : $default;
	}
	
	function getAs($key, $type, $default = null){
		$val = $this->get($key, $default);
		
		if(is_callable($type)){
			return call_user_func($type, $val);
		}else{
			switch(strtolower($type)){
				case "int":
				case "integer":
					return (int)$val;
				case "string":
				case "str":
					return (string)$val;
				case "bool":
				case "boolean":
					return (bool)$val;
				case "float":
				case "double":
					return (float)$val;
				default:
					return $val;
			}
		}
	}
}

usage.php

$p = new InputGetter([
	"a" => 1,
	"b" => "abc",
	"c" => "9",
	"d" => 0,
	"e" => "1,2,3,4,5",
	"f" => null,
]);

var_dump(
	$p->a, // 1
	$p->d, // 0
	$p->f, // NULL
	$p->z, // NULL
	$p->get("a"), // 1
	$p->get("b"), // "abc"
	$p->get("f", "default value"), // NULL
	$p->get("z", "default value"), // "default value"
	$p->getAs("a", "str"), // "1"
	$p->getAs("b", "float"), // 0
	$p->getAs("c", "int"), // 9
	$p->getAs("d", "bool"), // false
	$p->getAs("b", "foo"), // "abc"
	$p->getAs("c", "sqrt"), // 3
	$p->getAs("z", "boolean", "default value"), // true
	$p->getAs("e", function($e){
		return explode(",", $e);
	}) // ["1","2","3","4","5"]
);