Why does this array_walk function throw an error?
<pre><code>array_walk ($this-&gt;something, [$this, 'function_name'], $part_something);
</code></pre>

<blockquote>
  <p>Parse error: syntax error, unexpected '[' in /.../...php on line 67</p>
</blockquote>

<p>This works on my local test environment, but not on the server.</p>
