What is difference in <? and <?php : <p>I've got some old legacy code written in PHP 5.3. </p>

<p>All PHP blocks in this code are like</p>

<pre><code>&lt;? some_php_code_here ?&gt; 
</code></pre>

<p>and my Apache just ignores them, while works good with</p>

<pre><code>&lt;?php some_php_code_here ?&gt; 
</code></pre>

<p>Why old code contains invalid blocks, and why this old code works good on old server ? It's really hard to google something with so much special symbols, sorry for stupid question</p>
