Utility functions to help grab elements from arrays and objects, which some additions for handling $_REQUEST, $_POST, and $_GET as well

get-value-or-default.php

<?php

function get_value_or_default( $var, $object, $default = '', $sanitize_callback = '' ) {
	if( is_object( $object ) )
		$value = ! empty( $object->$var ) ? $object->$var : $default;
	elseif( is_array( $object ) )
		$value = ! empty( $object[$var] ) ? $object[$var] : $default;
	else
		$value = $default;
	
	if( is_callable( $sanitize_callback ) ) {
		if( is_array( $value ) )
			$value = array_map( $sanitize_callback, $value );
		else
			$value = call_user_func( $sanitize_callback, $value );
	}
	
	return $value;
}

function get_request_var( $var, $default = '', $sanitize_callback = '' ) {
	return get_value_or_default( $var, $_REQUEST, $default, $sanitize_callback );
}

function get_get_var( $var, $default = '', $sanitize_callback = '' ) {
	return get_value_or_default( $var, $_GET, $default, $sanitize_callback );
}
function get_post_var( $var, $default = '', $sanitize_callback = '' ) {
	return get_value_or_default( $var, $_POST, $default, $sanitize_callback );
}