Integers on the Intertubes

Some time ago, I wrote an application for my company. Like most weblets I’ve written, this used PHP and either MySQL or MSSQL for the backend. This particular application logged all phone calls. As part of the record, it would record the caller’s account number, which is a 5 or 6 digit integer.

So, I got a phone call from the director of our customer contact department this week. He was concerned about the reports. He made a decision last week that when a call came in that was a lead – in other words, a non-customer, that his people would fill the phone number from the caller ID into the account number field. But when he ran his export reports, he found that hisn techs had entered this phone number for ALL of the calls: 429-496-7295. That’s weird, he said. So he called me and asked why that was. I checked all the calls and most were from one woman, so my first instinct was “Check if her browser has autocomplete turned on”. But he swore that he tried it too and gotten the same result.

I checked the database and sure enough, it was right there: 429-496-7295, in all of the fields. So I went back to the code. In short, I took the input from the form, and declared it like this:

$accountnum = (int) $_POST['accountnum'];

Pretty straightforward: explicitly declare the type. So, I started my debugging by attempting to manually enter the data into the database. Sure enough: the account key field showed this: 4294967295.

So, I went back to the PHP and started by dumping out the raw SQL query:

INSERT INTO calls ('','x','x','x','4294967295','x','x');

What? So the database automatically converts it to this weird phone number and PHP does too? Suddenly it occured to me. One of the benefits of 64-bit computing is the ability to address more memory. There are limits to what can be done in 32-bit computing, and one is that integers have a limit! In this case, a database field called “integer” is limited to numbers between -2,147,483,648 and +2,147,483,647. It just so happens that the number is the same length as a US phone number – 10 digits. Changing the db field to “BIGINT” allowed me to manually run the SQL query and it worked. But the app still didn’t.

PHP’s int() and (int) $var syntaxes both conform to the integer limit. So I devised a work around:

$ac = $_POST['accountnum'];
if(!is_numeric($ac) { $ac = (int) $ac; }

It’s not gorgeous, but it will more than suffice for an internal app. We web programmers don’t usually have to deal with big integers, so it’s totally possible that web developers would never have had occasion to handle a situation like this. Here’s looking forward to native 64-bit for our next server, though.