dynamic keyword insertion

dki.php

<?php 

add_shortcode("dki", "dynamic_content");

/**
*   Usage: [dki key="city" default="London"]
*	Scenario 1: "city = Manchester" exists in the URL, function returns "Manchester"
*	Scenario 2: "city" does not appear in the UR, return "London"
*/
function dynamic_content($attributes) {
	$default = "";
	$return = "";
	$key = FALSE;
	if (!empty( $attributes['key'])) {
        $key = sanitize_text_field($attributes['key']);
	}
	if (!empty($attributes['default'])) {
        $default = sanitize_text_field($attributes['default']);
	}
	parse_str($_SERVER["QUERY_STRING"], $url_array);
	if ($key != FALSE && array_key_exists($key, $url_array)) {
		$return = sanitize_text_field($url_array[$key]);
	}
	else $return = $default;
	return esc_html($return);
}