Output date range between 2 dates.

date-range.php

<?php
function isValidTimestamp($timestamp) {
    return ((string) (int) $timestamp === $timestamp)
        && ($timestamp <= PHP_INT_MAX)
        && ($timestamp >= ~PHP_INT_MAX);
}

function get_date_range($startDate, $endDate) {
	$output = '';
	$diff = false;

	if ( !isValidTimestamp($startDate) ) {
		$startDate = strtotime($startDate);
	}

	if (!isValidTimestamp($endDate) ) {
		$endDate = strtotime($endDate);
	}

	if ( $startDate !== $endDate ) {
		$diff = true;
		if ( date('Y', $startDate) !== date('Y', $endDate) ) {
			$startDateFormat = date('F j, Y', $startDate);
			$endDateFormat = date('F j, Y', $endDate);
		}
		elseif ( date('F', $startDate) !== date('F', $endDate) ) {
			$startDateFormat = date('F j', $startDate);
			$endDateFormat = date('F j, Y', $endDate);
		}
		else {
			$startDateFormat = date('F j', $startDate);
			$endDateFormat = date('j, Y', $endDate);
		}
	} else {
		$startDateFormat = date('F j, Y', $startDate);
	}

	$output .= '<span class="date-start">' . $startDateFormat . '</span>';
	if ( $diff ) {
		$output .= '<span class="date-separator"> - </span>';
		$output .= '<span class="date-end">' . $endDateFormat . '</span>';
	}

	return $output;
}

function date_range($startDate, $endDate) {
	echo get_date_range($startDate, $endDate);
}