Reversable Encryption OR Storing Passwords online

<?php

function encrypt($str,$key){
  for($i = 0; $i < $key; $i++){
    // we want to encrypt each letter as many times as the $key val
    $n = 0;
    $newstr = "";
    while(isset($str{$n})){
      $newstr .= "!".base64_encode($str{$n});
      $n++;
    }
    $str = base64_encode($newstr);
  }
  return $str;
}

function decrypt($str,$key){
  for($i = 0; $i < $key; $i++){
    $str = base64_decode($str);
    $n = 0;
    $newstr = "";
    $bits = explode("!", $str); // we have split the string into seperate letters
    $fullstr = "";
    while(isset($bits[$n])){
      // decode a letter at a time
      $letter = base64_decode($bits[$n]);
      $fullstr .= $letter;
      $n++;
    }
    $str = $fullstr;
  }
  return $str;
}

if(isset($_POST['key']) && isset($_POST['str']) && isset($_POST['mode']) && ($_POST['mode'] == "encrypt" || $_POST['mode'] == "decrypt")){
  // we have vars
  $key = $_POST['key'];
  $str = $_POST['str'];
  $str = str_replace("!","",$str);
  $mode = $_POST['mode'];
  ?>
    <table>
      <tr>
        <td><textarea style="width: 850; height: 400" onFocus="this.select()"><?php if($mode == "encrypt"){ echo encrypt($str,$key); } else { echo decrypt($str,$key); } ?></textarea></td>
      </tr>
    </table>
  <?php
    }
    else{
  ?>
  
    <form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>" onSubmit="if(key.value>10){alert('Sorry, please keep the value of the key below 5, thanks.');key.value='5'};">
    
      String: <input name="str" /><br />
      KeyVal: <input name="key" /><br />
      Mode:   <select name="mode"><option value="encrypt">Encrypt</option><option value="decrypt">Decrypt</option></select><br />
      Submit: <input type="submit" value="Do it!" />
    
    <form>
  
  <?php
}

?>

<?php 
function dbConnect(){
	mysql_connect("localhost","*************","******")
		or die("Couldn't connect to the database because ".mysql_error());
	mysql_select_db("*************")
		or die("Couldn't select database because ".mysql_error());
}

function randomChar($length)
{
$password = "";
$possible = "0123456789abcdefghijklmnopqrstuvwxyz";
$i = 0;
while ($i < $length) {
$char = substr($possible, mt_rand(0, strlen($possible)-1), 1);
if (!strstr($password, $char)) {
$password .= $char;
$i++;
}

}
return $password;
}
$string = randomChar(rand(7,rand(8,rand(9,rand(rand(15,21),rand(22,37))))));
for ($i=0;$i<50;$i++){
$timeparts = explode(' ',microtime());
$thetime = $timeparts[1].substr($timeparts[0],1);

$md5_string = md5($string);

$timeparts = explode(' ',microtime());
$starttime = $timeparts[1].substr($timeparts[0],1);
$timeparts = explode(' ',microtime());
$endtime = $timeparts[1].substr($timeparts[0],1);
$difference[$i] = bcsub($endtime,$starttime,6);
}
$md5_endtime = (array_sum($difference))/50;

for ($i=0;$i<50;$i++){
$timeparts = explode(' ',microtime());
$thetime = $timeparts[1].substr($timeparts[0],1);

$base64_string = base64_encode($string);

$timeparts = explode(' ',microtime());
$starttime = $timeparts[1].substr($timeparts[0],1);
$timeparts = explode(' ',microtime());
$endtime = $timeparts[1].substr($timeparts[0],1);
$difference[$i] = bcsub($endtime,$starttime,6);
}
$base64_endtime = (array_sum($difference))/50;

echo "<b>Original String:</b>".$string."<br><br>";
echo "<b>Final md5 Time:</b> ";
echo number_format($md5_endtime, 70, '.', '');
echo "<br>";
echo "Final md5 String: ";
echo $md5_string;
echo "<br><br><b>Final base64 Time:</b> ";
echo number_format($base64_endtime, 70, '.', '');
echo "<br>";
echo "Final base64 String: ";
echo $base64_string;
echo "<br><br><b>Fastest:</b> ";
dbConnect();
if ($md5_endtime < $base64_endtime) 
{
	echo "MD5 <br><b>By</b> ".number_format($base64_endtime-$md5_endtime, 70, '.', '')." <b>seconds</b>.";
	$query = mysql_query("SELECT * FROM `base64_md5`");
	$row = mysql_fetch_array($query);
	$newval = $row['md5']+1;
	mysql_query("UPDATE `base64_md5` SET `md5` = '$newval' WHERE `id` =0 LIMIT 1 ;");
}
if ($md5_endtime > $base64_endtime) 
{
	echo "Base64 <br><b>By</b> ".number_format($md5_endtime-$base64_endtime, 70, '.', '')." <b>seconds</b>.";
	$query = mysql_query("SELECT * FROM `base64_md5`");
	$row = mysql_fetch_array($query);
	$newval = $row['base64']+1;
	mysql_query("UPDATE `base64_md5` SET `base64` = '$newval' WHERE `id` =0 LIMIT 1 ;");
}
echo "<center><b><br><br>Total Wins</b><hr></center><br><br>";
$query = mysql_query("SELECT * FROM `base64_md5`");
$row = mysql_fetch_array($query);
echo "<b>MD5:</b> ".$row['md5']."<br>";
echo "<b>Base64:</b> ".$row['base64'];
echo "<br><br><b>Last Calculation:</b> ".$row['date'];
mysql_query("UPDATE `base64_md5` SET `date` = '".date("Y-m-d h:i:s")."' WHERE `id` =0 LIMIT 1 ;"); 
mysql_close();