At first you have to change:
<input type="date" id="updateltext" name="listdate" value=""/>
to:
<input type="date" id="updateltext" name="list_date" value=""/>
To match what you have in your php code and apply it to the rest of the html inputs
then change:
WHERE product_id = ' .$id. '
to:
WHERE product_id = '$id'
Notice
Don’t forget to format for=”” in lable with id=”” in the input so as not to give you a different result
solved PHP sql database not updating after update query, indexes are not defined? [closed]