title: How can I split a string into an array?
body: <p>I try to split my string into an array. All strings between the calculation signs <code>+/*-</code>:</p>
  
  <pre><code>$keywords = preg_split("/[\s,-]*[+-*]+/", "quanity*price/2+tax");
  </code></pre>
  
  <p>This is what I try to achieve:</p>
  
  <pre><code>Array
  (
      [0] =&gt; quantity
      [1] =&gt; price
      [1] =&gt; tax
  )
  </code></pre>
  
  <p>But the result is an empty string.</p>