php, convert to hexadecimal integer

Question

My $_POST value contains css friendly hex color value, for example: #ffffff. In order to make it friendly towards the ColorJizz library, I should have it in hexadecimal integer value. The code below doesn't work. If I replace the $color_hex variable with a hard coded value for example: 0xffffff, it works.

include('colorjizz.php');   
$color_hex = '0x' . substr($_POST['color'], 1); 
$color = new Hex($color_hex);

This is most likely a very noob level problem, but after hitting my head to the wall for a quite few hours, I'd be grateful for any advice. Thank you.

ColorJizz may be hosted on code.google.com, but it is not "Google's" package. — jrn.ak
– jrn.ak, Commented Apr 14, 2011 at 0:49
What is the actual output of $color_hex in this example? I can't see an issue with it, assuming you are indeed getting a valid 6 digit hex value for $_POST['color'], WITH the # number sign character. — No Results Found
– No Results Found, Commented Apr 14, 2011 at 0:49
Hi Madmartigan, thanks for the reply. The actual $color_hex output in this example could be for example "0xFFFFFF" when the $_POST['color'] value has been #FFFFFF. Unfortunately ColorJizz doesn't like to work with it, most likely due to a wrong data type. — Dusty
– Dusty, Commented Apr 15, 2011 at 0:42

ikegami · Accepted Answer · 2011-04-14 00:53:25Z

2

"Hexadecimal integer value" doesn't make much sense. Hex is a representation of a number (thus a string), while integer value speaks of the machine format of a number.

If you want the number, a quick Google search found hexdec

$color = hexdec(substr($_POST['color'], 1));

It appears to ignore leading "junk", so you could even use

$color = hexdec($_POST['color']);

answered Apr 14, 2011 at 0:53

ikegami

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2 Comments

Dusty Over a year ago

Thank you for your reply ikegami. And oh, I had tried the hexdec method, but since it didn't output a value with a preceding "0x", for example "0xFFFFFF" I though it doesn't fit. But it sure does accept it. And it works with this now. Great! Thank you.

ikegami Over a year ago

@Tuomas, 0xFFFFFF is a numeric literal (a piece of the code) that produces the number 16,777,215. hexdec('FFFFFF') is another piece of code that produces the same number. Having the string 0xFFFFFF in a variable is much different than having 0xFFFFFF in the code.

Jonah · Accepted Answer · 2011-04-14 00:58:34Z

1

If you have a string containing a hexadecimal representation of a number and you want to have it as a integer you have to convert from hex to dec. If I get your question right.

$dec = hexdec("ff0000");

http://php.net/hexdec

edited Apr 14, 2011 at 0:58

Jonah

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answered Apr 14, 2011 at 0:52

Eliasdx

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Comments

Lucas Jones · Accepted Answer · 2011-04-14 00:51:49Z

0

In PHP, the data type for a hexadecimal integer and a decimal integer is the same; being able to type 0xDEAD in your source code is just syntactic sugar. Thus, you can use intval() to convert the form input to a normal PHP integer from a string:

$color_hex = intval(substr($_POST['color'], 1), 16);

The final parameter, 16, specifies that the input string is in hexadecimal.

answered Apr 14, 2011 at 0:51

Lucas Jones

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