controllo form php

Ragazzi dovrei controllare 3 campi in php 1) sarebbe il nome "minimo 4 caratteri da inserire" 2) l'email "minimo 5 caratteri" 3) per commentare "minimo 4 caratteri. si può fare ragazzi? vi posto il codice php

Codice PHP:

---

// -- form output ------------------------------------------------
$total = count($comments);
$counter = 1;
$html = '<div id="emContent">';
if($total > $CCOUNT){
$html .= '<div class="emShowAllComments" id="emShowAllComments"><a href="javascript:viewAllComments();">'.$lang['view'].' <span id="total_em_comments">'.$total.'</span> '.$lang['view2'].'</a> <noscript><em>This page needs JavaScript to display all comments</em></noscript></div>';
}
foreach($comments as $comment){
if($comment['sender_name']){
if($comment['sender_mail']){
$comment['sender_name'] = jsEncode($comment['sender_mail'], $comment['sender_name']);
}
$sender = '<span class="emSenderName">'.$comment['sender_name'].'</span>: ';
}else{
$sender = '';
}

$html .= '<div class="emComment" id="comment_'.$comment['id'].'" '.($counter < ($total - ($CCOUNT - 1))?'style="display:none"':'').'>
<div class="emCommentImage">
<img src="http://www.gravatar.com/avatar/'.gravatar($comment['sender_mail'], false).'" width="32" height="32" alt="Gravatar" />
</div>
<div class="emCommentText">
'.$sender.stripslashes($comment['comment_text']).'
</div>
<div class="emCommentInto">
'.strftime($DATEFORMAT,strtotime($comment['created'])).'
</div>
</div>';
$counter++;
}
$html .= '</div>';

$html .= '<div id="emAddComment">
<form method="post" action="commentanything/php/addComment.php" onsubmit="return false;">
<span '.($SHOWNAME?'':'').' id="emNameSpan">
<label for="addEmName">'.$lang['name'].':</label>
<input type="text" placeholder="'.$lang['enterName'].'" id="addEmName" name="sender_name" />
</span>

<span '.($SHOWMAIL?'':'').' id="emMailSpan">
<label for="addEmMail">'.$lang['mail'].':</label>
<input type="text" placeholder="'.$lang['enterMail'].'" id="addEmMail" name="sender_mail" />
</span>

<textarea placeholder="'.$lang['enterComment'].'" id="addEmComment" name="comment"></textarea>

<input type="text" name="email" value="" id="addEmPot" />
<input type="hidden" name="object_id" value="'.$object_id.'" />

<span class="emButton">
<input type="submit" class="emButton" id="emAddButton" value="'.$lang['comment'].'" onclick="addEMComment(\''.$object_id.'\')" />
</span>
</form>
</div>';


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grazie mille raga se mi aiutate