<?php
// Convert into a proper PHP array by trimming the extra stuff and exploding:
$var = '["continent"]["country"]["province"]';
$var = trim($var, '["');
$var = explode('"]["', $var);
// Apply native array functions...
$key = "country";
if (in_array($key, $var))
	// Do something if present
	echo "Present";
else
	echo "Not Present";
?>