PHP: still work even if not isset
<p>HTML new_password:</p>

<pre><code>   &lt;input name="new_password" type="password" maxlength="25" id="new_password" class="ModuleTextbox" onkeyup="var regex = new RegExp(/^.*(?=.{6,})(?=.*\d)(?=.*[aA-zZ@!¤&amp;amp;/()_?,.-]).*$/m); if(regex.test(this.value)) { pwok.style.visibility = 'visible'; } else { pwok.style.visibility = 'hidden'; }" style="width:200px;" /&gt;&amp;nbsp;&lt;img id="pwok" src="ok.png"
                            alt="R" style="visibility: hidden;" /&gt;
</code></pre>

<p>php after submit form:</p>

<pre><code>foreach($_POST as $key =&gt; $value) {
    $data[$key] = filter($value);
}
$pw_new = $data["new_password"];


   if(isset($pw_new)) {
echo "LOL";
}
</code></pre>

<p>even if i didnt write anything in the field, it echo's LOL, why's that?</p>
