Update over 100 fields in mysql - php

Question

i have 181 fields in my database named S1, S2....S181. I want to update these fields using values from inputs WITH name="S1", .....NAME="S181".
MY CODE IS
$S1=$_POST['S1'];
...
...
$S181=$_POST['S181'];
$sql=mysqli_query($conn,"update 'cap' set S1='$S1'......S181='$S181'")
I am trying something like
for ($i = 1; $i<=181; $i++ ) {
$(S$i)=$_POST['S$i'];
$sql = mysqli_query($conn, "UPDATE `cap4a` SET
S$i='$(S$i)'
WHERE IDID=".$id) or die (mysqli_error($conn));
}
Is there something wrong in the way I use S$i, because I am getting errors:
"Parse error: syntax error, unexpected '(', expecting variable (T_VARIABLE) or '$' in C:\xampp1\htdocs\update_cap4a.php on line 5" ?

Answer 1

I don't think it's a good idea to run 181 queries to alter the same row as you do. Instead, run one query that makes all required changes to the row. The code below will work for you:
$id = (int)$_POST['id'];//remove (int) if id IDID is a string
$snippets = [];//holds little snippets eg: S1='value1'
for($i=1;$i<=181;$i++){
$varname = "S$i"; //S1...S181
if(!isset($_POST[$varname])) continue;
$snippets[] = " $varname='$_POST[$varname]' ";
}
$sql = '"UPDATE cap SET '.implode(",",$snippets)." WHERE IDID=$id";
$result = mysqli_query($conn,$sql) or die (mysqli_error($conn));
I don't cover it in this snippet but you need to add at least two things before using this in production:
Proper error handling, for when your query fails
Prepared statements or escaped values to protect against SQL injection
Is there something wrong in the way I use S$i
To dynamically create a variable named S10 and set it to 'value' when $i=10, do:
$varname = "S$i";
$$varname = 'value'; // $$varname can also be referred to as $S10
See Variable Variables in the docs.

Answer 2

I would gave done it this way:
for ($i = 1; $i<=181; $i++) {
$key = 'S'.$i;
$value = $_POST[$key];
$update[] = "`{$key}` = '".$value."'";
$sql = mysqli_query($conn, "UPDATE `cap4a` SET ".join(",",$update)."
WHERE IDID=".$id) or die (mysqli_error($conn));
}