Retrieving and inserting multiple entries in MySQL/PHP - php

Question

I'm trying to create a form that retrieves data from a database and then allows me to add data to one column for multiple entries.
Every entry has an ID, a lot of other fields, and a category. I am trying to add these categories for every ID in the database using one form.
I came up with the solution below, but (of course)this only inserts the LAST entry in the form, because the variable ID is changed with every new row.
The form I have now shows me what I want to see, but it does not save it the way I need it to.
The question is, (how) can I make a form that has all entries in the database with a dropdown menu next to it,
lets me select the right category from the dropdown, and save it to the database?
The form:
$result = mysqli_query($con,"SELECT * FROM aw");
while($row = mysqli_fetch_array($result))
{
echo '<tr><td><input type="hidden" name="ID" value="'.$row[ID].'."> '.$row[ID].'</td><td>';
echo '
<select name="cat" onchange="this.form.submit()">
<option value="C1">category1</option>
<option value="C2"">category2</option>
</select></td></tr>
';
}
?>
<tr><td><input type="submit" title="SAVE" ></td></tr>
</form>
The insert.php
$sql="REPLACE INTO aw (ID,cat)
VALUES
('$_POST[ID]','$_POST[cat]')";
if (!mysqli_query($con,$sql))
{
die('Error: ' . mysqli_error($con));
}
mysqli_close($con);
?>
I changed my code according to Tom's answer and I now have the following:
This does print the values like they should be, but it still saves only the last entry into the database. I'm sure I must be missing something here..
$name = $_POST['ID'];
$category = $_POST['cat'];
foreach( $name as $key => $n ) {
$sql="REPLACE INTO aw (ID,cat)
VALUES
('$n','$category[$key]')";
print "The id is ".$n.", category is ".$category[$key]."<br>";
}

Answer 1

First of all, use PDO::Mysql, the SQL functions you are using are a bit deprecated and do not focus much on security. At the moment your code is vulnerable to SQL injections and your output is sensitive to XSS attacks (always sanitize output).
I was wrong, MySQL is deprecated but MySQLi is not! I do prefer using PDO::Mysql because of the range of databases it supports (MySQLi only supports a MySQL database, PDO::Mysql supports many more)
Now to your original question, you can create a sort of array. By making name="ID" to name="ID[]" and name="cat" to name="cat[]".
Now you can do
$name = $_POST['ID'];
$category = $_POST['cat'];
foreach( $name as $key => $n ) {
print "The id is ".$n.", category is ".$category[$key];
}

Answer 2

The problem is your using the name elements regardless of how many rows..
So name="ID" & name="cat" needs to change on each row or have an array type
you could use something like name="ID[]" as this would append/ create an array to $_POST['ID']... but you still would want to change your SQL query to handle each of these.
EDIT
If i understand, you want to be able to identify a row from the table so you can use that in the database?? One way todo this is when creating the table.. Give the TR a id/name attribute that is the row id from the database.
Then can simply know by checking that if your using the select menu from row #4, you check the id/name attribute of the current row and you have your database id.
<tr id='my_row_1'>
<td class='colName'>John</td>
<td class='colPhone'>1111</td>
<td class='colOther'>....</td>
</tr>
<tr id='my_row_2'>
<td class='colName'>Bill</td>
<td class='colPhone'>2222</td>
<td class='colOther'>....</td>
</tr>
<tr id='my_row_3'>
<td class='colName'>Roger</td>
<td class='colPhone'>3333</td>
<td class='colOther'>....</td>
</tr>
With something like the above, Say i had a button in on of the columns... When i click on that button.. all i have todo is find the parent TR and get its id value.... Then explode it by "_" and get the last piece to have the id..
So your PHP would generate the id easily... Also, using a form would not be the best case here.. Using multiple forms within a table is... wasteful... sort of ..
I would suggest more so, having a button that simple calls a js function which will then post/ajax/jquery what you need from that row.
--- Trying to understand exactly what you need??