Simple PHP md5 Cracker

// Simple Hash Cracker From Scratch no dictionary
// run "php -f filename.php <hash here> "
// modify PASSWORD_MAX_LENGTH if more than 8

<?php
set_time_limit(0);

function getmicrotime() {
   list($usec, $sec) = explode(" ",microtime());
   return ((float)$usec + (float)$sec);
}

$time_start = getmicrotime();

// algorithm of hash
// see http://php.net/hash_algos for available algorithms
define('HASH_ALGO', 'md5');

// max length of password to try
define('PASSWORD_MAX_LENGTH', 8);

$charset = 'abcdefghijklmnopqrstuvwxyz';
#$charset .= '0123456789';
#$charset .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
#$charset .= '~`!@#$%^&*()-_\/\'";:,.+=<>? ';
$str_length = strlen($charset);


// If no arguments given present usage info
if ($_SERVER["argc"] < 1) {
  print "Usage: attack.php <hash>\n";
  exit;
}

// Get MD5 checksum from command line
$hash_password = $_SERVER["argv"][1];

function check($password)
{
        global $hash_password, $time_start;

        if (hash(HASH_ALGO, $password) == $hash_password) {

                echo "\n\n" . "FOUND MATCH, password: " . $password . "\n\n";
                $time_end = getmicrotime();
                $time = $time_end - $time_start;
                echo "Found in " . $time . " seconds\n";
                exit;
        }
}


function recurse($width, $position, $base_string)
{
        global $charset, $str_length;

        for ($i = 0; $i < $str_length; ++$i) {
                if ($position  < $width - 1) {
                        recurse($width, $position + 1, $base_string . $charset[$i]);
                }
                check($base_string . $charset[$i]);
        }
}

echo "Target hash: " . $hash_password . "\n";
for ($i = 1; $i < PASSWORD_MAX_LENGTH + 1; ++$i) {
        echo "\n" . "Checking passwords with length:" .$i;
        $time_check = getmicrotime();
        $time = $time_check - $time_start;
        echo "\n" . "Runtime: " . $time . " seconds";
        recurse($i, 0, '');
}

echo "Execution complete, no password found\r\n";
?>