Someting wrong with script

[dan_t]

I was wondering if someone could tell me why this won't work.

 

<?php

 

echo hex_to_decimal('0xff');

echo "<br>\n";

 

echo hex_to_decimal('1e5a');

 

 

 

function hex_to_decimal ($hex)

{

 

$hex = strtolower($hex);

$hex = trim($hex);

 

if (substr($hex, 0, 2) == '0x')

$hex = substr($hex, 2);

 

$result = 0;

while ($hex != ' ')

{

 

$char = substr($hex, 0, 1);

if (ord($char) >= ord('a') and ord($char) <= ord('f'))

$val = 10 + (ord($char) - ord('a'));

else if (ord($char) >= ord('0') and ord($char) <= ord('9'))

$val = ord($char) - ord('0');

else

return INVALID_HEX_STRING;

 

$result = ($result * 16) + $val;

$hex = substr($hex, 1);

 

}

 

return $result;

 

}

 

 

?>

 

It just errors about  a problem with the invalid_hex_string constant.

[Alex]

'INVALID_HEX_STRING' isn't defined anywhere. You'd have to define it like..

 

define("INVALID_HEX_STRING", "Invalid hex string... etc..", true);

[dan_t]

<?php

 

echo hex_to_decimal('0xff');

echo "<br>\n";

 

echo hex_to_decimal('1e5a');

 

define("INVALID_HEX_STRING", "Invalid hex string", true);

 

function hex_to_decimal ($hex)

{

 

$hex = strtolower($hex);

$hex = trim($hex);

 

if (substr($hex, 0, 2) == '0x')

$hex = substr($hex, 2);

 

$result = 0;

while ($hex != ' ')

{

 

$char = substr($hex, 0, 1);

if (ord($char) >= ord('a') and ord($char) <= ord('f'))

$val = 10 + (ord($char) - ord('a'));

else if (ord($char) >= ord('0') and ord($char) <= ord('9'))

$val = ord($char) - ord('0');

else

return INVALID_HEX_STRING;

 

$result = ($result * 16) + $val;

$hex = substr($hex, 1);

 

}

 

return $result;

 

}

 

 

?>

 

I may have done this wrong, but this did not work either.

Is it possible something is not set in the "ini" file?

[blueman378]

it owuld be easier if you could tell us the exact errors?

[Philip]

The following works:

<?php
define("INVALID_HEX_STRING", " Invalid hex string", true);

echo hex_to_decimal('0xff').' :: '.hexdec('0xff');
echo "<br>\n";
echo hex_to_decimal('1e5a').' :: '.hexdec('1e5a');


function hex_to_decimal ($hex)
{
   $hex = strtolower($hex);
   $hex = trim($hex);
   
   if (substr($hex, 0, 2) == '0x') 
      $hex = substr($hex, 2);
      
      $result = 0;
      while ($hex != '')
      {
         
         $char = substr($hex, 0, 1);
         if (ord($char) >= ord('a') and ord($char) <= ord('f'))
            $val = 10 + (ord($char) - ord('a'));
         else if (ord($char) >= ord('0') and ord($char) <= ord('9'))
            $val = ord($char) - ord('0');
         else
            return INVALID_HEX_STRING;
            
         $result = ($result * 16) + $val;
         $hex = substr($hex, 1);
         
      }
      
   return $result;
   
}
?>

while ($hex != ' ') should have been while($hex != '') otherwise after it checks the last digit there is nothing left of the string but the loop will run until it finds a space.... which it won't thus returning INVALID HEX STRING

[vineld]

You do know about hexdec()? 

[dan_t]

No, sorry never heard of it. I wish I did but I'm not real good with PHP yet.

I do not if I ever wiil be, doesn't feel like it. :'(

[dan_t]

while ($hex != ' ') should have been while($hex != '') otherwise after it checks the last digit there is nothing left of the string but the loop will run until it finds a space.... which it won't thus returning INVALID HEX STRING

 

Man, I wish I understood that.

But you guys are amazing. I could have looked for the next ten years and never found that.

Thanks alot. I hope to someday understand some of this.

[Philip]

$hex = substr($hex, 1);

That will remove the first character from the string, which is placed at the end of your while loop. So, 1e5a would become e5a after the first pass of the loop. Whenever you run the loop 4 times, you are left with an empty variable, not a variable with the value of a space character. When you had it

while ($hex != ' ')

it would run that loop until hex was just a ' ' which would never happen.

And because it was empty, and your while loop looked for a space, when it came to the if statements, the empty $hex wasn't a character between 'a' and 'f'

if (ord($char) >= ord('a') and ord($char) <= ord('f'))

, and it wasn't a integer between '0' and '9'....

else if (ord($char) >= ord('0') and ord($char) <= ord('9'))

so it fell back to the last else statement - return an invalid hex string.

else   return INVALID_HEX_STRING;

[dan_t]

Thank you

I appreciate the help.