PHP check if a string contains only 0-9 and a few other chars
<p>I want to create a function where you check if a string contains only 0-9 /+*-{} (space) chars. This is similar to google's calculator query check.</p>

<pre><code>function is_calculation($str) {
if (???) {return true;}
return false;
}
</code></pre>

<p>it needs to be something like /[0-9 *-/+ [] {} () ]/</p>
