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

For debugging work with binary protocols, I needed a more traditional HEX dump, so I wrote this function:

function hex_dump($data, $newline="\n")
{
  static $from = '';
  static $to = '';
  
  static $width = 16; # number of bytes per line
  
  static $pad = '.'; # padding for non-visible characters
  
  if ($from==='')
  {
    for ($i=0; $i<=0xFF; $i++)
    {
      $from .= chr($i);
      $to .= ($i >= 0x20 && $i <= 0x7E) ? chr($i) : $pad;
    }
  }
  
  $hex = str_split(bin2hex($data), $width*2);
  $chars = str_split(strtr($data, $from, $to), $width);
  
  $offset = 0;
  foreach ($hex as $i => $line)
  {
    echo sprintf('%6X',$offset).' : '.implode(' ', str_split($line,2)) . ' [' . $chars[$i] . ']' . $newline;
    $offset += $width;
  }
}

This produces a more traditional HEX dump, like this:

hex_dump($data);

=>

 0 : 05 07 00 00 00 64 65 66 61 75 6c 74 40 00 00 00 [.....default@...]
10 : 31 42 38 43 39 44 30 34 46 34 33 36 31 33 38 33 [1B8C9D04F4361383]
20 : 46 34 36 32 32 46 33 39 32 46 44 38 43 33 42 30 [F4622F392FD8C3B0]
30 : 45 34 34 43 36 34 30 33 36 33 35 37 45 35 33 39 [E44C64036357E539]
40 : 43 43 38 44 35 31 34 42 44 36 39 39 46 30 31 34 [CC8D514BD699F014]

Note that non-visible characters are replaced with a period - you can change the number of bytes per line ($width) and padding character ($pad) to suit your needs. I included a $newline argument, so you can pass "<br/>" if you need to display the output in a browser.

echo bin2hex($string);

or:

for ($i = 0; $i < strlen($string); $i++) {
    echo str_pad(dechex(ord($string[$i])), 2, '0', STR_PAD_LEFT);
}

$string is the variable which contains input.