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Top Forums UNIX for Dummies Questions & Answers Magic numbers '&' operator problem Post 302536545 by Perderabo on Tuesday 5th of July 2011 05:41:27 PM
Old 07-05-2011
Xor is a bitwise operator:
0^0=0
0^1=1
1^0=1
1^1=0

If you have multiple 1 bits it is no longer a simple test.
Code:
0xd3 = 11010011
0xb1 = 10110001
       --------
0x62 = 01100010

It's not real obvious why you would do that. But the result is a match. Do you know C language? If so it is like:
Code:
a=0xd3;
b=0xb1;
if (a ^ b)   printf("match\n");

Make them both 0xb1 and the test will fail.
Code:
$
$ cat /tmp/mymagic
0 byte ^0xb1 filedetected
$ od -tx1 /tmp/x
0000000 b1 0a
0000002
$ file -m /tmp/mymagic /tmp/x
/tmp/x: ISO-8859 text
$

 

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DEBUG_PRINT_BACKTRACE(3)						 1						  DEBUG_PRINT_BACKTRACE(3)

debug_print_backtrace - Prints a backtrace

SYNOPSIS
void debug_print_backtrace ([int $options], [int $limit]) DESCRIPTION
debug_print_backtrace(3) prints a PHP backtrace. It prints the function calls, included/required files and eval(3)ed stuff. PARAMETERS
o $options - As of 5.3.6, this parameter is a bitmask for the following options: debug_print_backtrace(3) options +----------------------------+---------------------------------------------------+ |DEBUG_BACKTRACE_IGNORE_ARGS | | | | | | | Whether or not to omit the "args" index, and | | | thus all the function/method arguments, to save | | | memory. | | | | +----------------------------+---------------------------------------------------+ o $limit - As of 5.4.0, this parameter can be used to limit the number of stack frames printed. By default ($limit= 0) it prints all stack frames. RETURN VALUES
No value is returned. CHANGELOG
+--------+-----------------------------------------+ |Version | | | | | | | Description | | | | +--------+-----------------------------------------+ | 5.4.0 | | | | | | | Added the optional parameter $limit. | | | | | 5.3.6 | | | | | | | Added the optional parameter $options. | | | | +--------+-----------------------------------------+ EXAMPLES
Example #1 debug_print_backtrace(3) example <?php // include.php file function a() { b(); } function b() { c(); } function c(){ debug_print_backtrace(); } a(); ?> <?php // test.php file // this is the file you should run include 'include.php'; ?> The above example will output something similar to: #0 c() called at [/tmp/include.php:10] #1 b() called at [/tmp/include.php:6] #2 a() called at [/tmp/include.php:17] #3 include(/tmp/include.php) called at [/tmp/test.php:3] SEE ALSO
debug_backtrace(3). PHP Documentation Group DEBUG_PRINT_BACKTRACE(3)
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