not updating

[guitarzRus]

This code is just to update the receiptno by adding 1 and displaying the value of receiptno.
The only prob, it does neither.?? says "updated but NOT

Code: [Select]

<?php
$link = mysqli_connect("localhost", "root", "", "homedb"); 
// Check connection
if($link === false){ die("ERROR: Could not connect. " . mysqli_connect_error()); }

$id = &#39;id&#39;;
$receiptno=&#39;&#39;;

/* Perform a query, check for error */
$sql = "UPDATE control SET 
receiptno = &#39;$receiptno&#39; + 1 where id=&#39;$id&#39;";
echo $receiptno;
 if(mysqli_query($link, $sql)){ echo "updated"; } 
else { echo "ERROR: Could not able to execute $sql. " . mysqli_error($link); }
 // Close connection
mysqli_close($link); 
?>