user14316: I make a JSON call to
https://blockchain.info/tobtc?currency=USD&value=1
This is a free api with a request limit.
I have just received my api_code via email. This is blockchain.info's example of how to use it

Once approved the API Code can be passed to all requests in the "api_code" parameter e.g. https://blockchain.info?api_code=$your_code

I am guessing that they mean with PHP (because of the dollar sign) as when I type into my address bar
https://blockchain.info/tobtc?api_code=000my0-api00-code-0000-000000000&currency=USD&value=1

The data does not any look different when I use the api code with the dollar
https://blockchain.info/tobtc?api_code=$000my0-api00-code-0000-000000000&currency=USD&value=1

Though I am unsure of how to tell what is the correct way as I can access this free api with and without an api code (with a request limit). How do I tell if I am adding it correctly?

user19606: The first one is correct.
https://blockchain.info/tobtc?api_code=000my0-api00-code-0000-000000000&currency=USD&value=1
However, the particular call you are using (/tobtc) is public and thus needs no api_code attached.
https://blockchain.info/tobtc?currency=USD&value=1

14316: <p>I make a JSON call to</p>

<p><a href="https://blockchain.info/tobtc?currency=USD&amp;value=1" rel="nofollow">https://blockchain.info/tobtc?currency=USD&amp;value=1</a></p>

<p>This is a free api with a request limit.</p>

<p>I have just received my api_code via email. This is blockchain.info's example of how to use it</p>

<blockquote>
  <p>Once approved the API Code can be passed to all requests in the "api_code" parameter e.g. <a href="https://blockchain.info?api_code=" rel="nofollow">https://blockchain.info?api_code=</a>$your_code</p>
</blockquote>

<p>I am guessing that they mean with PHP (because of the dollar sign) as when I type into my address bar</p>

<pre><code>https://blockchain.info/tobtc?api_code=000my0-api00-code-0000-000000000&amp;currency=USD&amp;value=1
</code></pre>

<p>The data does not any look different when I use the api code with the dollar</p>

<pre><code>https://blockchain.info/tobtc?api_code=$000my0-api00-code-0000-000000000&amp;currency=USD&amp;value=1
</code></pre>

<p>Though I am unsure of how to tell what is the correct way as I can access this free api with and without an api code (with a request limit). How do I tell if I am adding it correctly?</p>
 19606: <p>The first one is correct.<br>
<a href="https://blockchain.info/tobtc?api_code=000my0-api00-code-0000-000000000&amp;currency=USD&amp;value=1" rel="nofollow">https://blockchain.info/tobtc?api_code=000my0-api00-code-0000-000000000&amp;currency=USD&amp;value=1</a></p>

<p>However, the particular call you are using (/tobtc) is public and thus needs no api_code attached.</p>

<p><a href="https://blockchain.info/tobtc?currency=USD&amp;value=1" rel="nofollow">https://blockchain.info/tobtc?currency=USD&amp;value=1</a></p>
