Posts are not saved through the checkbox - php

Question

I have tried in many ways to fix it but without success.
I'm trying to sort categories through the checkbox but it does not work. The post is made public during editing but the checkbox is not active and after the post update is checkbox removes the id and the post loses from the category.
<form name="addpost" method="post" enctype="multipart/form-data">
<div class="form-group m-b-20">
<label for="exampleInputEmail1">Category</label>
<br>
<?php
$ret=mysqli_query($con,"select id,CategoryName from tblcategory where Is_Active=1");
while($result=mysqli_fetch_array($ret))
{
?>
<input type="checkbox" name="category" id="category" value="<?php echo htmlentities($result['id']);?>"><?php echo htmlentities($result['CategoryName']);?><br>
<?php } ?>
<button type="submit" name="update" class="waves-effect waves-light pull-right butoni">Update </button>
</div>
</form>

Answer 1

This:
<input type="checkbox" name="category" id="category" value="<?php echo htmlentities($result['id']);?>"><?php echo htmlentities($result['CategoryName']);?><br>
is placed in a loop... so there are more than one of these yes?!
We can't use the same id, and name for multiple inputs of a form or in html ... instead :
<input type="checkbox" name="category[]" id="category<?php echo $result['id'];?>" value="<?php echo htmlentities($result['id']);?>"><?php echo htmlentities($result['CategoryName']);?><br>
this will make things appear in one after the other...
if you want the box to be checked add an if in the loop
if($result['something'] should be checked){ ?>
<input type="checkbox" name="category[]" id="category<?php echo $result['id'];?>" value="<?php echo htmlentities($result['id']);?> checked "><?php echo htmlentities($result['CategoryName']);?><br><?php
} else {
<input type="checkbox" name="category[]" id="category<?php echo $result['id'];?>" value="<?php echo htmlentities($result['id']);?>"><?php echo htmlentities($result['CategoryName']);?><br><?php
}
just fix the:
if($result['something'] should be checked){rest of the code}
to be correct according the when checkbox should be checked and when not.
For checkbox to be checked we add a checked in the input line.