function generatePassword ($length = 16)
	{
	
	  // start with a blank password
	  $password = "";
	
	  // define possible characters
	  $possible = "0123456789bcdfghjkmnpqrstvwxyz"; 
		
	  // set up a counter
	  $i = 0; 
		
	  // add random characters to $password until $length is reached
	  while ($i < $length) { 
	
		// pick a random character from the possible ones
		$char = substr($possible, mt_rand(0, strlen($possible)-1), 1);
			
		// we don't want this character if it's already in the password
		if (!strstr($password, $char)) { 
		  $password .= $char;
		  $i++;
		}
	
	  }
	
	  // done!
	  return $password;
	
	}

Generate password

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