Class could be something like:

<?php require_once 'Zend/Filter/Interface.php'; class Zend_Filter_StringPad implements Zend_Filter_Interface { const TYPE_BOTH = 'both'; const TYPE_LEFT = 'left'; const TYPE_RIGHT = 'right'; /** * Padding length * @var string */ protected $_length; /** * Padding characters * @var string */ protected $_string; /** * Padding type * @var string */ protected $_type; public function __construct($length, $string = ' ', $type = self::PADDING_RIGHT) { $this->setLength($length); $this->setString($string); $this->setType($type); } /** * Retrieve padding length * * @return int */ public function getLength() { return $this->_length; } /** * Retrieve padding characters * * @return string */ public function getString() { return $this->_string; } /** * Retrieve padding type * * @return string */ public function getType() { return $this->_type; } /** * Set padding length * * @param int $length * @return Zend_Filter_StringPad */ public function setLength($length) { $this->_length = (int) $length; return $this; } /** * Set padding characters * * @param string $string * @return Zend_Filter_StringPad */ public function setString($string) { $this->_string = (string) $string; return $this; } /** * Set padding type * * @param string $type * @return Zend_Filter_StringPad */ public function setType($type) { switch ($type) { case self::TYPE_BOTH: case self::TYPE_LEFT: case self::TYPE_RIGHT: $this->_type = $type; break; default: throw new Zend_Filter_Exception('Padding type is invalid'); } return $this; } /** * Converts our pad type consts to STR_PAD_* consts * * @return string */ protected function _getType() { switch ($this->_type) { case self::TYPE_LEFT: return STR_PAD_LEFT; case self::TYPE_RIGHT: return STR_PAD_RIGHT; default: return STR_PAD_BOTH; } } /** * Pad a string to a certain length with another string * * @param string $value * @return string */ public function filter($value) { $pad = ''; if (strlen($value) > 0) { $pad = str_pad($value, $this->_length, $this->_string, $this->_getType()); } return $pad; } } ?>