What is the PHP numeric array key limit - php

Question

I am having a problem with an array changing the value of keys on me. In the example I'm providing below it starts out ok, but at some point php is turning my string into an integer and changing that integer when inserting it into another array as a key.
Code
-----------------
$fund = '01';
$division = '1';
$gl_transactions[$fund] = array();
$glint = array($division=>array('gl_cash_account'=>'1800001040000000'));
print chr(10).'1:'.chr(10);
print_r($glint);
$gl = $glint[$division]['gl_cash_account'];
print chr(10).'2:'.chr(10);
print $gl;
$gl_transactions[$fund][$gl]['description'] = 'MTS DISBURSEMENTS';
print chr(10).'3:'.chr(10);
print_r($gl_transactions);
Expected output
---------------
1:Array([1] => Array([gl_cash_account] => 1800001040000000 ))
2:1800001040000000
3:Array([01] => Array([1800001040000000] => Array([description] => MTS DISBURSEMENTS)))
Actual output
---------------
1:Array([1] => Array([gl_cash_account] => 1800001040000000 ))
2:1800001040000000
3:Array([01] => Array([1721082880] => Array([description] => MTS DISBURSEMENTS)))
notice the index changed from 1800001040000000 to 1721082880
Obsticles
These big numbers are G/L Account numbers and cannot be changed to smaller numbers. We have tens of thousands of pieces of code, over a million lines of code in our product and cannot go through every bit of it to find where this may be an issue and rewrite it. This is just a generic example of something that we do in many places, building multidimensional arrays using data from a database. I can simply cast the variable as a string when inserting into the array to fix the above example, but backfilling 1M+ lines of code is not a viable option.
On my development machine I run php 5.3 MSSQL, Windows, and IIS. I do not get this error with the above code but I do get it when simply setting a variable as an integer and then inserting it into an array as a key. i.e. $gl = 1800001040000000; $ar[$gl] = 1; print_r($ar); Now we don't cast a variables to integers in our software, but in the first example php converts it on it's own at some point when it's building the last array when ran on some of our clients systems.
So my questions are:
What is the exact limit of a numeric array key.
Is there a way to increase this.
Has this been fixed or increased in later versions of php beyond 5.2
Other notes
Our software works with several databases, several browsers, window and linux, apache and IIS. We have hundreds of customers using the software all with their own unique setup. Most of our customers are on php 5.2 currently and upgrading them is not possible at this point because of deprecated functions used in our software.

Answer 1

My guess is that you are limited by the maximum value of an integer since PHP will automatically cast strings with valid integer values being used as array keys to integers. The PHP manual indicates the limits for integers will vary by system, but the big issue is 32-bit systems vs. 64-bit systems in determining upper limit.
http://php.net/manual/en/language.types.integer.php
The maximum integer value on a system can be read from PHP_INT_MAX constant.

Answer 2

I see there is no accepted answer here, and certainly the OP has moved on from this. I was losing my keys in an array like this (from Snowmed CT):
static function getNemsisProcedures() {
$nemsis[445828009] = 'Assessment Advanced Spinal Assessment (i.e., spinal clearance)';
$nemsis[425058005] = 'Assessment Orthostatic Vital Signs';
// etc....
$nemsis[89666000] = 'Cardiac CPR, Manual';
$nemsis[450661000124102] = 'Cardiac Defibrillation, AED'; // TAKE NOTE
$nemsis[426220008] = 'Cardiac Defibrillation, Manual';
// a lot more etc...
The issue was with "Cardiac Defibrillation, AED" because the key as an integer 450661000124102 was greater than PHP_MAX_INT (2147483647 in my case).
Solution: Use string keys where applicable.
In my case, I did not require the keys to be integers, and to prevent a large commit in git, I simply gave the affected Snowmed CT Procedure values keys with type string by quoting them:
static function getNemsisProcedures() {
$nemsis[445828009] = 'Assessment Advanced Spinal Assessment (i.e., spinal clearance)';
$nemsis[425058005] = 'Assessment Orthostatic Vital Signs';
// etc....
$nemsis[89666000] = 'Cardiac CPR, Manual';
// KEY IS GREATER THAN PHP_MAX_INT - USE QUOTES:
$nemsis['450661000124102'] = 'Cardiac Defibrillation, AED';
$nemsis[426220008] = 'Cardiac Defibrillation, Manual';
// a lot more etc...