Best practice: Handle first/last item in foreach

Question

Many times I ran into a situation like this

$str = '';
foreach($arr as $item)
{
    $str .= $item . ',';
}

The result would be something like $str = item1,item2,item3,. But I dont want the , at the end.

Now there are some ways to get rid of the ,.
E.g.

• use substr() to cut of the ,.

• write a function to detect the last item and alter the body of the loop to

  $str .= $item;  
  if(!last($item)) 
     $str .= ',';
  

  I think this is good readable, but the programm checks every item if it is the last one, which is obviously only one time the case.

• use implode(',', $arr) (But lets assume that this is not possible. Think about a more complex body of the loop)

What would be best practice to handle the last (or the first) item in a foreach loop?

Answer 1

This might also be a way:

$last = end($arr);   // returns the last item and sets the internal pointer to the end
unset($arr[key($arr)])   // deletes the last item from the array
$str = '';
foreach($arr as $item)
{
    $str .= $item . ',';
}
$str .= $last;

This does not check or assign anything additional in the loop, but I think it is not a good readable way.

Answer 2

You can also use rtrim to remove last unwanted character(s)

$str = rtrim($str, ',');

Answer 3

In languages that do not have a join-like method, this is what I've used (and seen used) for a while.

result = ""
delim = ""
foreach(string in array)
   result += delim + string
   delim = ","

^{(Apply to your favorite language)}

In your case using PHP, it would look like

$str = "";
$delim = "";
foreach($arr as $item) {
    $str .= $delim + $item;
    $delim = ",";
}

Answer 4

Follow this Example it may solve your hurdle.

$arr = array(1,2,3,4,5,6,7);
$copy = $arr;
foreach ($arr as $val) {
    echo $val;
    if (next($copy )) {
        echo ','; // Add comma for all elements instead of last
    }
}