title: How to check the query string of my current url for a specific key-value pair?
body: <p>How I can identify in PHP if my current URL contains this text <code>special_offer=12</code>.
  For example, if my domain URL is <code>http://www.example.com/newproducts.html?special_offer=12</code> then echo something.</p>
  
  <p>Alternatively, the domain can be <code>http://example.com/all-products.html?at=93&amp;special_offer=12</code></p>
  
  <p>This text will always be the same: <code>special_offer=12</code>.</p>