duplicating javscript math errors

I am trying to replicate javascript maths functions in php. I have been successful with everything up to additions.

Here are some examples, I can't see a pattern here that indicates exactly how javascript is screwing it up. Does anyone know **exactly** what javascript is doing?

I assume it's converting the integers into floating points and losing accuracy there, but I don;t know what floating point it's converting into, I also don't see why it would make a difference wha the first figure in a large number is when doing an addition, but apparently it does???

In the examples it's the 1000's and lower that get screwed up.

Example 1, add x20575940379279400 to 13510798882111488, where x is 1 to 9
Results:
134086739261390880
234086739261390880
334086739261390900
434086739261390900
534086739261390900
634086739261390800
734086739261390800
834086739261390800
934086739261390800

Example 2, add x34086739261390900 to 2814749767106560, where x is 1 to 9
Results:
136901489028497460
236901489028497470
336901489028497500
436901489028497500
536901489028497500
636901489028497400
736901489028497400
836901489028497400
936901489028497400

Example 3, add x36901489028497500 to 9895604649984, where x is 1 to 9
Results
136911384633147490
236911384633147500
336911384633147460
436911384633147460
536911384633147460
636911384633147500
736911384633147500
836911384633147500
936911384633147500

Example 4, add x611686018427388000 to 648518346341351400, where x is 1 to 9
Results
2260204364768739300
3260204364768739300
4260204364768739300
5260204364768739000
6260204364768739000
7260204364768739000
8260204364768739000
9260204364768740000
10260204364768740000

This is because the long datatype is not existent in JavaScript. For that, you will have to use an additional library. Just in case you don't want to go there, the included files are also attached.

Code:

---

<div style="font: 14px monospace;">
<script type="text/javascript" src="mathcontext.js"></script>
<script type="text/javascript" src="bigdecimal.js"></script>
<script type="text/javascript">
for (var i = 1; i <= 9; i++) {
  var firstNumber = parseInt(i + "20575940379279400", 10);
  var secondNumber = 13510798882111488;
  var finalNumber = parseInt(firstNumber, 10) + secondNumber;

  var v1 = new BigDecimal(firstNumber.toString());
  var v2 = new BigDecimal(secondNumber.toString());
  finalNumber = v1.add(v2);

  document.write("&nbsp; " + firstNumber + "<br />+&nbsp; " + secondNumber);
  document.write("<br />--------------------<br />&nbsp; " + finalNumber)
  document.write("<br /><br />");
}
</script>
</div>

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