Date to timestamp

<?php
    // convert dd/mm/yyyy to unix timestamp (at midnight)
    static function date_to_timestamp( $datestring ) {
        //if ( Z1_AEC_EVENT_DEBUG ) error_log("date_to_timestamp( $datestring )");
        $parts = explode( '/', $datestring );
        if ( count( $parts ) != 3 )
            return 0;
        $timestamp = strtotime( $parts[2] . '/' . $parts[1] . '/' . $parts[0] );
        //if ( Z1_AEC_EVENT_DEBUG ) error_log("date_to_timestamp( $datestring ) returning $timestamp");
        return $timestamp;
    }

    static function timestamp_to_date( $timestamp, $format = 'd/m/Y' ) {
        //if ( Z1_AEC_EVENT_DEBUG ) error_log("timestamp_to_date( $timestamp )");
        $timestamp = intval( $timestamp );
        if ( empty( $timestamp ) )
            return '';
        $datestring = date($format, $timestamp);
        //if ( Z1_AEC_EVENT_DEBUG ) error_log("timestamp_to_date( $timestamp ) returning $datestring");
        return $datestring;
    }
?>