How can I get a hex dump of a string in PHP?

Question

I\'m investigating encodings in PHP5. Is there some way to get a raw hex dump of a string? i.e. a hex representation of each of the bytes (not characters) in a string?

Answer 1

It's years later, but in case others are searching for this too, I took the liberty to modify mindplay.dk's code to make it accept various options and simulate the output of the BSD command hexdump -C file:

/**
* Dumps a string into a traditional hex dump for programmers,
* in a format similar to the output of the BSD command hexdump -C file.
* The default result is a string.
* Supported options:
* 
*   line_sep        - line seperator char, default = "\n"
*   bytes_per_line  - default = 16
*   pad_char        - character to replace non-readble characters with, default = '.'
* 
*
* @param string $string
* @param array $options
* @param string|array
*/
function hex_dump($string, array $options = null) {
    if (!is_scalar($string)) {
        throw new InvalidArgumentException('$string argument must be a string');
    }
    if (!is_array($options)) {
        $options = array();
    }
    $line_sep       = isset($options['line_sep'])   ? $options['line_sep']          : "\n";
    $bytes_per_line = @$options['bytes_per_line']   ? $options['bytes_per_line']    : 16;
    $pad_char       = isset($options['pad_char'])   ? $options['pad_char']          : '.'; # padding for non-readable characters

    $text_lines = str_split($string, $bytes_per_line);
    $hex_lines  = str_split(bin2hex($string), $bytes_per_line * 2);

    $offset = 0;
    $output = array();
    $bytes_per_line_div_2 = (int)($bytes_per_line / 2);
    foreach ($hex_lines as $i => $hex_line) {
        $text_line = $text_lines[$i];
        $output []=
            sprintf('%08X',$offset) . '  ' .
            str_pad(
                strlen($text_line) > $bytes_per_line_div_2
                ?
                    implode(' ', str_split(substr($hex_line,0,$bytes_per_line),2)) . '  ' .
                    implode(' ', str_split(substr($hex_line,$bytes_per_line),2))
                :
                implode(' ', str_split($hex_line,2))
            , $bytes_per_line * 3) .
            '  |' . preg_replace('/[^\x20-\x7E]/', $pad_char, $text_line) . '|';
        $offset += $bytes_per_line;
    }
    $output []= sprintf('%08X', strlen($string));
    return @$options['want_array'] ? $output : join($line_sep, $output) . $line_sep;
}

and this is a hex dump of a small file:

00000000  89 50 4e 47 0d 0a 1a 0a  00 00 00 0d 49 48 44 52  |.PNG........IHDR|
00000010  00 00 00 10 00 00 00 10  02 03 00 00 00 62 9d 17  |.............b..|
00000020  f2 00 00 00 09 50 4c 54  45 04 04 04 99 99 cc d7  |.....PLTE.......|
00000030  d7 d7 2a 66 f6 6b 00 00  00 38 49 44 41 54 78 9c  |..*f.k...8IDATx.|
00000040  63 08 05 02 06 24 22 0b  44 24 01 89 ac a4 69 4b  |c....$".D$....iK|
00000050  19 1a 16 68 70 31 74 29  75 2c 42 22 1a 16 75 00  |...hp1t)u,B"..u.|
00000060  c5 22 33 96 32 74 86 46  4c 65 58 19 1a 35 15 61  |."3.2t.FLeX..5.a|
00000070  00 00 df be 19 a6 2e 62  80 87 00 00 00 00 49 45  |.......b......IE|
00000080  4e 44 ae 42 60 82                                 |ND.B`.|
00000086

and this is the phpunit test:

assertFileExists($file);
        include($file);
        $this->assertTrue(function_exists(static::FUNCTION_NAME));
    }

    public function testString() {
        $func = static::FUNCTION_NAME;
        $data = base64_decode(static::DATA_BASE64);
        if (!is_string($data)) {
            throw new Exception('Unable to decode base64 encoded test data');
        }
        $dump = $func($data);
        //var_export($dump);
        $this->assertTrue(is_string($dump));
        $this->assertEquals($dump, join("\n", $this->expect) . "\n");
    }

}


if (isset($argv)) {
    $func = Test::FUNCTION_NAME;
    require_once($func . '.php');
    if (count($argv) < 2) {
        print "Pass arguments file, from, length.\n";
    }
    else {
        $file = $argv[1];
        if (!file_exists($file)) {
            die("File not found: $file\n");
        }
        $from   = isset($argv[2]) && preg_match('/^\d{1,9}$/', $argv[2]) ? intval($argv[2]) : null;
        $len    = isset($argv[3]) && preg_match('/^\d{1,9}$/', $argv[3]) ? intval($argv[3]) : filesize($file);
        $h = fopen($file, 'r');
        if ($from) {
            fseek($h, $from);
        }
        $data = fread($h, $len);
        fclose($h);
        $dump = hex_dump($data);
        print $dump;
        //$dump = hex_dump($data, array('want_array' => true));
        //print_r($dump);
    }
}