PHP array argument validation: Checks that required variables exist within a scope

expect.fn.php

<?php

/**
 * Checks that required variables exist within a scope(array or object)
 * If any required variable is not present, an exception is thrown.
 * Also allows an input of default variables, which are set if not set beforehand
 *
 * Example usage:
 * function foo($args){
 *     expect($args, ['a', 'b', 'c']); // throws error
 * }
 * foo(['a'=>1,'b'=>2,'d'=>3]);
 * 
 * @license    http://opensource.org/licenses/gpl-license.php  GNU Public License
 * @author     Joshua McKenzie <josh@ia.lc>
 * @param  mixed  &$scope            array or object to check against
 * @param  array  $required_varnames list of variable names to check
 * @param  array  $default_vars      array of keys to check, and values to set
 * @param  class  $exception         exception class
 */
function expect(&$scope=null, $required_varnames=null, $default_vars=null, $exception = '\Exception'){
	if(is_null($scope))$scope = $GLOBALS;
	if(is_array($scope)){
		if(!is_null($required_varnames)){
			foreach($required_varnames as $varname){
				if(!isset($scope[$varname]))
					throw new $exception('Missing expect argument '.$varname);
			}
		}
		if(!is_null($default_vars)){
			foreach($default_vars as $key=>$value){
				if(!isset($scope[$key]))
					$scope[$key] = $value;
			}
		}
	} else if(is_object($scope)){
		if(!is_null($required_varnames)){
			foreach($required_varnames as $varname){
				if(!isset($scope->{$varname}))
					throw new $exception('Missing expect argument '.$varname);
			}
		}
		if(!is_null($default_vars)){
			foreach($default_vars as $key=>$value){
				if(!isset($scope->{$key}))
					$scope->{$key} = $value;
			}
		}
	} else throw new $exception('Invalid expect scope');
}