title: PHP - Variable inside variable?
body: <p>$bookA = "123";
      $crack = "A";</p>
  
  <p>I want to do something similar to this:</p>
  
  <pre><code>echo $book$crack;
  </code></pre>
  
  <p>Such that the output is <strong>123</strong>.</p>
  
  <p>What is the correct syntax for the echo command?</p>
  
  <p>Thanks.</p>