<?php
/**
 * Zend Framework (http://framework.zend.com/)
 *
 * @link      http://github.com/zendframework/zf2 for the canonical source repository
 * @copyright Copyright (c) 2005-2013 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd New BSD License
 */

namespace Zend\Filter;

use Zend\Stdlib\StringUtils;

class Digits extends AbstractFilter
{
    /**
     * Defined by Zend\Filter\FilterInterface
     *
     * Returns the string $value, removing all but digit characters
     *
     * If the value provided is non-scalar, the value will remain unfiltered
     * and an E_USER_WARNING will be raised indicating it's unfilterable.
     *
     * @param  string $value
     * @return string|mixed
     */
    public function filter($value)
    {
        if (null === $value) {
            return null;
        }

        if (!is_scalar($value)){
            trigger_error(
                sprintf(
                    '%s expects parameter to be scalar, "%s" given; cannot filter',
                    __METHOD__,
                    (is_object($value) ? get_class($value) : gettype($value))
                ),
                E_USER_WARNING
            );
            return $value;
        }

        if (!StringUtils::hasPcreUnicodeSupport()) {
            // POSIX named classes are not supported, use alternative 0-9 match
            $pattern = '/[^0-9]/';
        } elseif (extension_loaded('mbstring')) {
            // Filter for the value with mbstring
            $pattern = '/[^[:digit:]]/';
        } else {
            // Filter for the value without mbstring
            $pattern = '/[\p{^N}]/';
        }

        return preg_replace($pattern, '', (string) $value);
    }
}
