assign hexadecimal values to variables

[rajoo.sharma]

Hello,

 

assigning a constant by prefixing 0x to a variable stores it as hex value, not as a string.

$a=0xa1; //this 161 in decimal

 

but if I already have a value somewhere, then how do I assign it same as above?

$some_value = "a10ce2";

$a= substr($some_value, 0, 2); //this is not same as $a=0xa1;

 

I've to use it for XOR checksum, I already have values in a text file, so I'll read a line and use XOR to validate.

 

$a=0x87;$b=0xa0;$c=0x03;$d=0x00;$e=0x0c;$f=0x28;

echo $a ^ $b ^ $c ^ $d ^ $e ^ $f; //perfectly returns 0;

 

but this is a constant assigned to a variable, when we already have values:

 

$values = "87a003000c28";

 

$a=substr($values, 0, 2);

$b=substr($values, 2, 2);

$c=substr($values, 4, 2);

$d=substr($values, 6, 2);

$e=substr($values, 8, 2);

$f=substr($values, 10, 2);

echo $a^$b^$c^$d^$e^$f; //does not return 0;

 

Please help

 

Regards

 

 

 

 

[lur]

$values = "87a003000c28";

$a=hexdec(substr($values, 0, 2));
$b=hexdec(substr($values, 2, 2));
$c=hexdec(substr($values, 4, 2));
$d=hexdec(substr($values, 6, 2));
$e=hexdec(substr($values, 8, 2));
$f=hexdec(substr($values, 10, 2));
echo $a^$b^$c^$d^$e^$f;

[kenrbnsn]

You probably want to use the base_convert() function to convert the strings from hexadecimal to decimal and then perform the  XOR function:

<?php
$values = '87a003000c28';
$tmp = array();
for($i=0;$i<strlen($values);$i += 2)
     $tmp[] = base_convert(substr($values,$i,2),16,10);
$xor = 0;
foreach($tmp as $val) {
    echo '$val = ' . sprintf("%0X",$val) . "<br>\n";   //debug
    $xor = $xor ^ $val;
    echo sprintf("%0X",$xor) . "<br>\n"; }    //debug
echo $xor . "\n";
?>

 

Ken