<?
 
$l='a';//Set the starting letter
for($i=0;$i<26;$i++){//Cycle through all of the letters of the alphabet a-z
$key[$i]=$l;//Load the array with lowercase variables at position $i
$l++;//Increment the letter
}
for($x=0;$x<5;$x++){//Cycle through this five times. The more you cycle through this loop the more likely a number will appear.
for($n=0;$n<10;$n++){//Cycle through the numbers 0-9
$key[$i]=$n;//Load the array with number variables at position $i
$i++;//Increment the array key
}
}
$u='A';//Set the starting letter
for($c=0;$c<26;$c++){//Cycle through all of the letters of the alphabet A-Z
$key[$i]=$u;//Load the array with uppercase variables
$i++;//Increment the array key
$u++;//Increment the letter
}
 
$i--;//Subtract the last incrementation of $i because it's not indexed
 
$str='';
for($strlength=0;$strlength<20;$strlength++){//Generate the random string 20 characters long
//$r = rand(0,$i);	//Generate a random number from the available $i interger
$r = rand()&$i;//Generate a random number from the available $i interger using bitwise
$str .= $key[$r];//Concatenate the random variable
}
 
echo $str;//Show the random string
?>