defined a constant but memory has no change
<p>I tried to compare the constants and variables used in memory, but found a strange phenomenon.</p>

<p>test code:</p>

<pre><code>&lt;?php
var_dump( memory_get_usage() );  // int(129100)
// I don't understand: I don't do someting but why there has the changed
var_dump( memory_get_usage() );  // int(129156)  
var_dump( memory_get_usage() );  // int(129156)

define('hello', 'WORLD');
// why here hasn't changed
var_dump( memory_get_usage() );  // int(129156)

$hello = 'WORLD';
var_dump( memory_get_usage() );  // int(129304)
?&gt;
</code></pre>
