<?php

$array = array(11,12,15,16,17,18,22,23,24);
$break_start = array();

//range finder
for ($i=0; $i<sizeof($array); $i++) {
	$current = $array[$i]; 
	$previous = $array[$i-1];
	if ($current==($previous+1)) { 
		//no break points are found 
	} else { 
		//return break points with keys intact
	    array_push($break_start, $i);
	}
	
}

for ($i=0; $i<sizeof($break_start); $i++) {
	$key = $break_start[$i];
	$next_key = $break_start[$i+1];

	//if last iteration
	if ($i==sizeof($break_start)-1) { 
		echo "Range: ".$array[$key]." - ".$array[count($array)-1]." \n"; 
		} 
	else { 
		echo "Range: ".$array[$key]." - ".$array[$next_key-1]." \n";	
		}
}