php method argument type hinting with question mark (?type) : <p>I just felt on pieces of php (symfony/laravel) code using question mark in method type hints :</p>

<pre><code>public function functionName(?int $arg = 0)
</code></pre>

<p>In other occasions the <strong>?type</strong> was not the last one, but I did not find any of these with no default yet.</p>

<p>Problem is, I cannot find any information about this, and I checked :</p>

<ul>
<li>here : <a href="http://php.net/manual/en/migration70.new-features.php" rel="noreferrer">http://php.net/manual/en/migration70.new-features.php</a></li>
<li>and here : <a href="http://php.net/manual/en/migration71.new-features.php" rel="noreferrer">http://php.net/manual/en/migration71.new-features.php</a></li>
<li>and here : <a href="http://php.net/manual/en/functions.arguments.php" rel="noreferrer">http://php.net/manual/en/functions.arguments.php</a></li>
</ul>

<p>And same with 7.2, but since the code only requires 7.1, it seems rather normal.</p>

<p>I also googled, and searched here, but either this is not documented or the question marks topic is defeating search engines.</p>

<p>So I feel a little dumb now, and I would really appreciate if someone could enlighten me on the signification of this question mark in method signatures arguments.</p>

<p>Thanks</p>
