title: is_numeric() vs. is_float() vs. is_int()
body: <p>My understanding is...</p>
  
  <p>if <code>is_numeric($input) === true</code></p>
  
  <p>then either </p>
  
  <p><code>is_float($input) === true</code> OR </p>
  
  <p><code>is_int($input) === true</code> OR </p>
  
  <p><code>$input === 0</code> OR </p>
  
  <p><code>$input</code> is a numeric string (meaning it'd satisfy one of the first 3 if it weren't wrapped in quotes).</p>
  
  <p>Is that accurate? Are there other differences?</p>