Implode sorted number array to string with commas and merge consecutive integers into hyphenated range expressions [duplicate]

Question

I would like to implode an array, but with one difference. I would like to merge intervals with a - sign. How can this be done? (The array is ordered!)

Examples:

array(1,2,3,6,8,9) => "1-3,6,8-9"
array(2,4,5,6,8,10) => "2,4-6,8,10"

Answer 1

This should work for you:

First for every iteration we simply append the current number of the iteration to the $result string:

$result .= $arr[$i];

After this we check in a while loop if there exists a next element in the array(1) and it follows up the number from the current iteration(2). We do that until the condition evaluates as false:

//(1)Check if next element exists     (2)Check if next element follows up the prev one
      ┌───────┴───────┐    ┌───────────┴────────────┐      
while(isset($arr[$i+1]) && $arr[$i] + 1 == $arr[$i+1] && ++$range)
    $i++;

Then we check if we have a range (e.g. 1-3) or not. If yes then we append the dash and the end number of the range to the result string:

if($range)
    $result .= "-" . $arr[$i];

At the end we also check if we are at the end of the array and don't need to append a comma anymore:

if($i+1 < $l)
    $result .= ",";

Code:

<?php

    $arr = array(1,2,3,6,8,9);
    $result = "";
    $range = 0;

    for($i = 0, $l = count($arr); $i < $l; $i++){

        $result .= $arr[$i];

        while(isset($arr[$i+1]) && $arr[$i] + 1 == $arr[$i+1] && ++$range)
            $i++;

        if($range)
            $result .= "-" . $arr[$i];

        if($i+1 < $l)
            $result .= ",";

        $range = 0;   

    }

    echo $result;

?>

output:

1-3,6,8-9

Answer 2

    $oldArray=array(2,4,5,6,8,10);

    $newArray=array();


    foreach($oldArray as $count=>$val){
        if($count==0){
            //begin sequencing
            $sequenceStart=$sequenceEnd=$val;
        }

        if($val==$sequenceEnd+1){
            $sequenceEnd=$val;
            continue;
        }else{
            if($sequenceEnd==$val){
                //do nothing
                continue;
            }


        }

        //new sequence begins 
        //save new sequence
        if($sequenceStart==$sequenceEnd){
            //sequnce is a single number
            $newArray[]=$sequenceEnd;
        }else{
            $newArray[]=$sequenceStart.'-'.$sequenceEnd;
        }

        //reset sequence
        $sequenceStart=$sequenceEnd=$val;
    }

    //new sequence begins 
    //save new sequence
    if($sequenceStart==$sequenceEnd){
        //sequnce is a single number
        $newArray[]=$sequenceEnd;
    }else{
        $newArray[]=$sequenceStart.'-'.$sequenceEnd;
    }

    //reset sequence
    $sequenceStart=$sequenceEnd=$val;



    return implode(',', $newArray);