title: PHP: how to check if string is not numeric, but can contain spaces?
body: <p>The goal is to validate a number that is numeric and may or may not contain spaces.</p>
  
  <p>Eg, both '1800 123 456' and '1800123456' are acceptable.</p>
  
  <p>Checking to see if it is not numeric is easy:</p>
  
  <pre><code>if(!is_numeric($phone_number)) {
    //display error message
  }
  </code></pre>
  
  <p>But I am stuck as to how to pass it with spaces.</p>
  
  <p>Would anyone be able to point me in the right direction with this?</p>