How many days does 1 month represent in PHP?
<p>I see there is strange problem in php with month addition and subtraction. </p>

<p><strong>My questions are:</strong>
<li>does 1 month have an equivalent in days ?
<li>if yes, is this a common standard in all programing languages ?</p>

<p><strong>A few examples:</strong></p>

<pre><code>echo date('Y-m-d',strtotime('2011-03-31 -1 months')); //2011-03-03
echo date('Y-m-d',strtotime('2011-03-30 -1 months')); //2011-03-02
echo date('Y-m-d',strtotime('2011-03-29 -1 months')); //2011-03-01
echo date('Y-m-d',strtotime('2011-03-28 -1 months')); //2011-02-28
</code></pre>
