ขอความช่วยเหลือหน่อยคะ random ค่า3ช่องถ้าทุกช่องเป็นเลขเดียวกันให้ echo win

<?php
 $str = '1234567890';
 $shuffled = str_shuffle($str);

if (isset($_POST['submit'])) {
	
	
 ?>

 <center><form name="test" action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>" method="POST">
<input type="text" name="textbox1" style="width:50px; height: 50px; text-align: center" value="<?php echo rand(0,9); ?>" />
<input type="text" name="textbox2" style="width:50px; height: 50px; text-align: center" value="<?php echo rand(0,9); ?>" />
<input type="text" name="textbox3" style="width:50px; height: 50px; text-align: center" value="<?php echo rand(0,9); ?>" /><br><br>
<input type="submit" name="submit" id="submit" value="Submit">
</form></center>
<?

$a=$_POST['texebox1'];
$b=$_POST['texebox2'];
$c=$_POST['texebox3'];
if($a==$b&&$c==$b){

echo "win";}
}else{
 ?>
  <center><form name="test" action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>" method="POST">
<input type="text" name="textbox" style="width:50px; height: 50px; text-align: center" value="<?php echo substr($shuffled ,0,1); ?>" />
<input type="text" name="textbox" style="width:50px; height: 50px; text-align: center" value="<?php echo substr($shuffled ,0,1); ?>" />
<input type="text" name="textbox" style="width:50px; height: 50px; text-align: center" value="<?php echo substr($shuffled ,0,1); ?>" /><br><br>
<input type="submit" name="submit" id="submit" value="Submit">
</form></center>
 <?
 }
 ?>