how to update multiple checkbox - php

Question

I want to update the subject and other fields by adding multiple subjects, but the issue is it only saves one of subject which I have checked.
How can I solve this issue ?
Below is my code :
<?php
$status = "";
if(isset($_POST['new']) && $_POST['new']==1)
{
$host="localhost";//host name
$username="root"; //database username
$word="";//database word
$db_name="tuichk";//database name
$tbl_name="data"; //table name
$con=mysqli_connect("$host", "$username", "$word","$db_name")or die("cannot connect");//connection string
$id=$_REQUEST['id'];
$name =$_REQUEST['name'];
$stu_ic = $_REQUEST['stu_ic'];
$address = $_REQUEST['address'];
$contact = $_REQUEST['contact'];
$checkbox1=$_REQUEST['subject'];
$chk="";
$update="update data set name='".$name."', stu_ic='".$stu_ic."', address='".$address."', contact='".$contact."', sub='".$checkbox1."' where id='".$id."'";
mysql_query($update) or die(mysql_error());
$status = "Record Updated Successfully. </br></br><a href='view.php'>View Updated Record</a>";
echo '<p style="color:#FF0000;">'.$status.'</p>';
}else {
?>
this is my html form
<form name="form" method="post" action="">
<input type="hidden" name="new" value="1" />
<input name="id" type="hidden" value="<?php echo $row['id'];?>" />
<p><input type="text" name="name" placeholder="Enter Name" required value="<?php echo $row['name'];?>" /><input type="text" name="stu_ic" placeholder="Enter Student IC" required value="<?php echo $row['stu_ic'];?>" /></p>
<p><input type="text" name="address" placeholder="Enter Address" required value="<?php echo $row['address'];?>" /><input type="text" name="contact" placeholder="Enter Contact" required value="<?php echo $row['contact'];?>" /></p>
<div style="text-align:center">
<div style="width:400px;border-radius:6px;margin:0px auto">
<table border="1">
<tr>
<td colspan="2">Select Subject:</td>
</tr>
<tr>
<td>Bahasa Melayu</td>
<td><input type="checkbox" name="subject" value="Bahasa Melayu"></td>
</tr>
<tr>
<td>English</td>
<td><input type="checkbox" name="subject" value="English"></td>
</tr>
<tr>
<td>Mathematics</td>
<td><input type="checkbox" name="subject" value="Mathematics"></td>
</tr>
<tr>
<td>Science</td>
<td><input type="checkbox" name="subject" value="Science"></td>
</tr>
<tr>
<td>Sejarah</td>
<td><input type="checkbox" name="subject" value="Sejarah"></td>
</tr>
<tr>
<td>Geography</td>
<td><input type="checkbox" name="subject" value="Geography"></td>
</tr>
<tr>
<td>Additional Mathematics</td>
<td><input type="checkbox" name="subject" value="Additional Mathematics"></td>
</tr>
<tr>
<td>Chemistry</td>
<td><input type="checkbox" name="subject" value="Chemistry"></td>
</tr>
<tr>
<td>Physics</td>
<td><input type="checkbox" name="subject" value="Physics"></td>
</tr>
<tr>
<td>Biology</td>
<td><input type="checkbox" name="subject" value="Biology"></td>
</tr><tr>
<td>Principle Of Accounting</td>
<td><input type="checkbox" name="subject" value="Principle Of Accounting"></td>
</tr><tr>
<td>Ekonomi Asas</td>
<td><input type="checkbox" name="subject" value="Ekonomi Asas"></td>
</tr><tr>
<td>Perdagangan</td>
<td><input type="checkbox" name="subject" value="Perdagangan"></td>
</tr>
</table>
</div>
</form>

Answer 1

HTML input should be
<input type="checkbox" name="subject[]" value="Subject1">
<input type="checkbox" name="subject[]" value="Subject2">
In PHP have many options.
Option 1:
save subjects as string
$subjects = implode(',', $_POST['subject']);
retrieve as string and convert to array
$subjects = explode(',', $field);
Option 2: can save as JSON and retrieve as JSON and decode it.

Answer 2

this is my code inc html form:
<?php
$status = "";
if(isset($_POST['new']) && $_POST['new']==1)
{
$host="localhost";//host name
$username="root"; //database username
$word="";//database word
$db_name="tuichk";//database name
$tbl_name="data"; //table name
$con=mysqli_connect("$host", "$username", "$word","$db_name")or die("cannot connect");//connection string
$id=$_REQUEST['id'];
$name =$_REQUEST['name'];
$stu_ic = $_REQUEST['stu_ic'];
$address = $_REQUEST['address'];
$contact = $_REQUEST['contact'];
$checkbox1=$_REQUEST['subject'];
$subjects = implode(',', $_POST['subject']);
$subjects = explode(',', $field);
$chk="";
$update="update data set name='".$name."', stu_ic='".$stu_ic."', address='".$address."', contact='".$contact."', sub='".$checkbox1."' where id='".$id."'";
mysql_query($update) or die(mysql_error());
$status = "Record Updated Successfully. </br></br><a href='view.php'>View Updated Record</a>";
echo '<p style="color:#FF0000;">'.$status.'</p>';
}else {
?>
<div>
<form name="form" method="post" action="">
<input type="hidden" name="new" value="1" />
<input name="id" type="hidden" value="<?php echo $row['id'];?>" />
<p><input type="text" name="name" placeholder="Enter Name" required value="<?php echo $row['name'];?>" /><input type="text" name="stu_ic" placeholder="Enter Student IC" required value="<?php echo $row['stu_ic'];?>" /></p>
<p><input type="text" name="address" placeholder="Enter Address" required value="<?php echo $row['address'];?>" /><input type="text" name="contact" placeholder="Enter Contact" required value="<?php echo $row['contact'];?>" /></p>
<div style="text-align:center">
<div style="width:400px;border-radius:6px;margin:0px auto">
<table border="1">
<tr>
<td colspan="2">Select Subject:</td>
</tr>
<tr>
<td>Bahasa Melayu</td>
<td><input type="checkbox" name="subject[]" value="Bahasa Melayu"></td>
</tr>
<tr>
<td>English</td>
<td><input type="checkbox" name="subject[]" value="English"></td>
</tr>
<tr>
<td>Mathematics</td>
<td><input type="checkbox" name="subject[]" value="Mathematics"></td>
</tr>
<tr>
<td>Science</td>
<td><input type="checkbox" name="subject[]" value="Science"></td>
</tr>
<tr>
<td>Sejarah</td>
<td><input type="checkbox" name="subject[]" value="Sejarah"></td>
</tr>
<tr>
<td>Geography</td>
<td><input type="checkbox" name="subject[]" value="Geography"></td>
</tr>
<tr>
<td>Additional Mathematics</td>
<td><input type="checkbox" name="subject[]" value="Additional Mathematics"></td>
</tr>
<tr>
<td>Chemistry</td>
<td><input type="checkbox" name="subject[]" value="Chemistry"></td>
</tr>
<tr>
<td>Physics</td>
<td><input type="checkbox" name="subject[]" value="Physics"></td>
</tr>
<tr>
<td>Biology</td>
<td><input type="checkbox" name="subject[]" value="Biology"></td>
</tr><tr>
<td>Principle Of Accounting</td>
<td><input type="checkbox" name="subject[]" value="Principle Of Accounting"></td>
</tr><tr>
<td>Ekonomi Asas</td>
<td><input type="checkbox" name="subject[]" value="Ekonomi Asas"></td>
</tr><tr>
<td>Perdagangan</td>
<td><input type="checkbox" name="subject[]" value="Perdagangan"></td>
</tr>
</table>
</div>
</form>
<p><input name="submit" type="submit" value="Update" /></p>
</form>
<?php } ?>