Something causes incorrect output from PHP's date()
<p>This is my code.</p>

<pre><code>$arrivDate = $_POST['arrival_date'];
echo $arrivDate; //Print correctly
echo date("Y/m/d", strtotime($arrivDate)) ; // every time print 1969/12/31
echo date("Y/m/d", strtotime('.$arrivDate.')) ; // every time print 1969/12/31
</code></pre>

<p>but if i put like this, it is print correctly</p>

<pre><code>echo date("Y/m/d", strtotime("05/08/2019")); // Print like this --&gt; 2019/08/05 (This is correct)
</code></pre>

<p>My question is if i put hard coded value, it is print very well. but i cant put a variable to it. evry time print a garbage value. im sure that $_POST['arrival_date'] part has no any problem because according to my 2nd line, the correct value is shown.
Please tell me the reason for this....</p>
