function create_key(&$cnnDB){
	$letters = range('A','Z');
	$numbers = range(0,9);
	$all = array_merge($numbers,$letters);
	$foundkey = false;
	while(!$foundkey){
		for($i=0;$i<5;$i++){
			$num = rand(0,count($all)-1);
			$key .= $all[$num];
			$total += $num;
		}
	
		//Replace Oh with Zero, I with one
		$key = str_replace(
					array('O','I'),
					array('0','1'),
					$key
		);
		
		//make checksum
		$key .= $all[($total % count($all))];
		
		$key = str_replace(
					array('O','I'),
					array('0','1'),
					$key
		);
		
		$SQL = 'select C_Key from customers where C_Key = "'.$key.'"';
		$result = $cnnDB->GetRow($SQL);
		if(count($result) == 0){
			$foundkey = true;
		}
	}

	return $key;
}

Create Unique Code Replacing Lookalike Characters

code

PHP