Prettify a range of dates.

get_pretty_date_range.php

<?php
/**
 *  Prettify a range of dates.
 *
 *  @param   mixed   $start         The start date
 *  @param   mixed   $end           The end date
 *  @param   string  $format        A date() string for formatting if the dates match
 *  @param   string  $format_day    A date() string for formatting if they are different days
 *  @param   string  $format_month  A date() string for formatting if they are different months
 *  @param   string  $format_year   A date() string for formatting if they are different years
 *  @param   string  $divider       The divider for parsing the formats
 *  @return  string                 A prettified date() string for the date range
 */
function get_pretty_date_range( $start=null, $end=null, $format='F j, Y', $format_day='F j -- j, Y', $format_month='F j -- F j, Y', $format_year='M j, Y', $divider='--' ) {
    $diff_month = false;
    $diff_year = false;

    // Make sure a start and end date are supplied
    if( empty( $start ) || empty( $end ) ) {
        return 'You need to supply a start and end date.';
    }

    if( ! is_valid_timestamp( $start ) ) {
        $start = strtotime( $start );
    }

    if( ! is_valid_timestamp( $end ) ) {
        $end = strtotime( $end );
    }

    // Check if the dates match
    if ( date( 'Ymd', $start ) == date( 'Ymd', $end ) ) {
        return date( $format, $start );
    } else {
        // Check if months differ
        if( date( 'm', $start ) != date( 'm', $end ) ) {
            $diff_month = true;
        }

        // Check if years differ
        if( date( 'Y', $start ) != date( 'Y', $end ) ) {
            $diff_year = true;
        }
    }

    // Different years
    if( $diff_year ) {
        return date( $format_year, $start ).' - '.date( $format_year, $end );
    }

    // Different months
    if( $diff_month ) {
        $month = explode( $divider, $format_month );
        return date( trim( $month[0] ), $start ).' - '.date( trim( $month[1] ), $end );
    }

    // Different days
    $day = explode( $divider, $format_day );
    return date( trim( $day[0] ), $start ).' - '.date( trim( $day[1] ), $end );
}

function is_valid_timestamp( $strTimestamp ) {
    return ( (string)(int)$strTimestamp == $strTimestamp )
        && ( $strTimestamp <= PHP_INT_MAX )
        && ( $strTimestamp >= ~PHP_INT_MAX );
}