Class for generating strings of arbitrary length (free customization)

Customizable length, letters, numbers, upper and lower case

/*
 * Class for generating random strings, which only contains numbers and uppercase and lowercase letters by default
 * @author Jerry
 */

class randomString {
 /*
 * Character settings contained in the generated string
 */

 const NUMERIC_ONLY = 1; //Only contains numbers
 const LETTER_ONLY = 2; //Only contains letters
 const MIXED = 3; //Mix numbers and letters

 /*
 * The variables passed in by the user are the length of the string; the letters it contains; whether it contains uppercase letters
 */

 protected $length, $type, $upper;

 /*
 * Parameter initialization
 * @param int,$length The length of the string
 * @param const,$type The type of the generated string
 * @param boolean,$upper Whether it contains uppercase letters
 */

 public function __construct($length = 16, $type = self::MIXED, $upper = true) {
 $this->length = $length;
 $this->type = $type;
 $this->upper = $upper;
 }

 / *
 * Called when the object is converted to a string
 * @return string
 */

 public function __toString() {
 return $this->pickUpChars();
 }

 /*
 * Generate a random string
 * @global $type
 * @return string,$string
 */

 public function pickUpChars() {
 switch ($this->type) {
 case self::NUMERIC_ONLY:
 $raw = '0123456789' ;
 break;
 case self::LETTER_ONLY:
 $raw = 'qwertyuioplkjhgfdsazxcvbnm' .
 'QWERTYUIOPLKJHGFDSAZXCVBNM';
 break;

 default:
 $raw = 'qwertyuioplkjhgfdsazxcvbnm' .
 'QWERTYUIOPLKJHGFDSAZXCVBNM' .
 '0123456789';
 break;
 }
 $string = '';
 for ($index = 0; $index < $this->length; $index++)
 $string .= substr($raw, mt_rand(0, strlen($ raw) - 1), 1);
 if (!$this->upper)
 $string = strtolower($string);
 return $string;
 }

}

//echo new randomString(170, randomString::MIXED, TRUE).'';