user3436467 - 1 year ago 105

PHP Question

I am extracting a serial from a digital certificate using the built in openssl library, however i am having trouble converting this number to hex with precision.

The extracted number is originally in decimal but i need to have it in hex.

The number I am trying to convert is: 114483222461061018757513232564608398004

Here is what I've tried:

- did not work, it returns:
`dechex()`

`7fffffffffffffff`

The closest I could get was this function from the php.net page but it does not convert the whole number on part of it.

`function dec2hex($dec) {`

$hex = ($dec == 0 ? '0' : '');

while ($dec > 0) {

$hex = dechex($dec - floor($dec / 16) * 16) . $hex;

$dec = floor($dec / 16);

}

return $hex;

}

echo dec2hex('114483222461061018757513232564608398004');

//Result: 5620aaa80d50fc000000000000000000

Here is what I am expected:

- Decimal number: 114483222461061018757513232564608398004
- Expected hex: 5620AAA80D50FD70496983E2A39972B4

I can see the correction conversion here:

https://www.mathsisfun.com/binary-decimal-hexadecimal-converter.html

I need a php solution.

Answer Source

The problem is that `The largest number that can be converted is ... 4294967295`

- hence why it's not working for you.

This answer worked for me during a quick test, assuming you have bcmath installed on your server, **and you can obtain the number as a string to start with**. If you can't, i.e. it begins life as numeric variable, you'll immediately reach PHP's float limit.

```
// Credit: joost at bingopaleis dot com
// Input: A decimal number as a String.
// Output: The equivalent hexadecimal number as a String.
function dec2hex($number)
{
$hexvalues = array('0','1','2','3','4','5','6','7',
'8','9','A','B','C','D','E','F');
$hexval = '';
while($number != '0')
{
$hexval = $hexvalues[bcmod($number,'16')].$hexval;
$number = bcdiv($number,'16',0);
}
return $hexval;
}
```

Example:

```
$number = '114483222461061018757513232564608398004'; // Important: already a string!
var_dump(dec2hex($number)); // string(32) "5620AAA80D50FD70496983E2A39972B4"
```

Ensure you pass a string into that function, not a numeric variable. In the example you provided in the question, it looks like you can obtain the number as a string initially, so should work if you have bc installed.