<?php
//To Pull 7 Unique Random Values Out Of AlphaNumeric

//removed number 0, capital o, number 1 and small L
//Total: keys = 32, elements = 33
$characters = array(
"A","B","C","D","E","F","G","H","J","K","L","M",
"N","P","Q","R","S","T","U","V","W","X","Y","Z",
"1","2","3","4","5","6","7","8","9");

//make an "empty container" or array for our keys
$keys = array();

//first count of $keys is empty so "1", remaining count is 1-6 = total 7 times
while(count($keys) < 6) {
    //"0" because we use this to FIND ARRAY KEYS which has a 0 value
    //"-1" because were only concerned of number of keys which is 32 not 33
    //count($characters) = 33
    $x = mt_rand(0, count($characters)-1);
    if(!in_array($x, $keys)) {
       $keys[] = $x;
   }
}

/* debug */ print_r($keys);

foreach($keys as $key){
   $random_chars .= $characters[$key];
}
echo $random_chars;
?>

Array
(
    [0] => 21
    [1] => 29
    [2] => 20
    [3] => 18
    [4] => 17
    [5] => 11
)
X6WUTM