PHP automatically removes the zeros that i need in an identification string - php

Question

In a table, the primary field is a Char(12) field called ribiid, whose format is RB##########,
It needs to auto-increment it self, and for that i have prepared the following code:
function getid() {
global $connection;
$idquery = "SELECT ribiid FROM systems ORDER BY ribiid DESC LIMIT 1";
$idsave = mysqli_query($connection, $idquery);
$idresult = mysqli_fetch_assoc($idsave);
$idalpha = substr($idresult['ribiid'], 0, 2);
$idnumeric = substr($idresult, 2);
$newidnumeric = $idnumeric + 1;
$newid = $idalpha . $newidnumeric;
return $newid;
}
Now for testing I manually entered a row in cmd with id = RB0000000000, the next entry that I submit through my webpage using php, should have been RB0000000001, but it is coming RB1.
How can I fix this, this is my first web database. Thanks

Answer 1

Your problem is that when adding 1 to $idnumeric PHP needs to treat it as a number. Leading zeroes in numbers do not make sense, so they are discarded.
To keep the zeroes you can use sprintf format the resulting (incremented) number:
$newid = sprintf("%s%010d", $idalpha, $newidnumeric);
However, using code like this is not a really good idea
There's an issue with this code though: it's subject to a race condition. Consider what could happen if two instances of the script run in parallel:
Instance A Instance B
T |
i | Reads ribiid RB..001 Reads ribiid RB..001
m | Generates next id RB..002 Generates next id RB..002
e v Writes RB..002 to DB
Writes RB..002 to DB => OOPS
As you see this situation will result in instance B failing to insert a record due to the use of a duplicate primary key. To solve this problem you need to eliminate the race condition, which you could do in one of several ways:
Use an AUTO_INCREMENT column for the PK instead of manually inserting values. Although this means you can no longer have the "RB" prefix as part of the key, you can move it to a different column and have the PK be a combination of these two columns.
LOCK TABLES ribiid while the insertion is taking place (note that the lock needs to cover all of the process, not just the getid function). Locking tables is something you normally want to avoid, but if inserts are not frequent it's a usable practical solution.

Answer 2

You could try something like this:
$newid = $idalpha . str_pad($newidnumeric, 10, '0', STR_PAD_LEFT);
This will add zeros to reach the ten chars.

Answer 3

You can padd the numeric string again using the following function:
function pad_number($number, $pad=10){
$pad_zero = $pad - strlen($number.'');
$nstr = '';
for($i =0; $i< $pad_zero; $i++){
$nstr .="0";
}
$nstr .= $number;
return $nstr;
}
You can use in your code this function as:
$newid = $idalpha . pad_number($newidnumeric);