PHP implode with increment value

Question

Is there any way to add an increment value while imploding an array?

This is the piece of code I'd like to have the increment value:

$entries = '<ul class="repeatData"><li class="listEntry1">' . implode('</li><li class="listEntry'. $countme .'">', $data) . '</li></ul>';

I'd like somehow to make the variable $countme increment every time it implodes each array value, if this is even possible.

$countme = $countme + 1 ; – underscore Oct 21 '13 at 16:37 — underscore, Oct 21 '13 at 16:37
@samitha Doesn't work. I tried it. – otinanai Oct 21 '13 at 16:39 — otinanai, Oct 21 '13 at 16:39

Tom Macdonald · Accepted Answer · 2013-10-21T17:19:45.767

8

You cannot do this with implode, but look into applying an anonymous function to the array. You can probably do what you want with not much more code.

$entries = '<ul class="repeatData">';
$countme = 1;

array_walk($data, function ($element) use (&$entries, &$countme) { 
    $entries .= '<li class="listEntry'. $countme .'">'. $element . '</li>';
    $countme++;
});
$entries .= "</ul>";

Explanation: I have written an anonymous function, told it about $entries and $counter (so it is a closure, in fact) so that it can modify them from inside its scope, and passed it to array_walk, which will apply it to all elements of the array.

edited Oct 21 '13 at 17:19

answered Oct 21 '13 at 16:43

Tom Macdonald

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I would really appreciate an example here. Your suggestion sound fast and promising. – otinanai Oct 21 '13 at 16:46
A simple `for` loop would do the same here, but faster.. But however, more important is that it will not solve the problem. It is requested to implode `$data` but in your case it will just append the `
..` to every(!) element of `$data`

hek2mgl

Oct 21 '13 at 16:53

Yup, I just fixed that bug. Trying to get my answer in too fast, mea culpa! – Tom Macdonald Oct 21 '13 at 16:56

2

And yes a for loop is a faster answer, but closures are more fun, and a good technique for less tractable problems than html lists. I'm future-proofing the OP! – Tom Macdonald Oct 21 '13 at 16:57

2

He wants to join the elements of the array into an html list. That is what I have done. I do not understand what the issue is. I know what implode() does. – Tom Macdonald Oct 21 '13 at 17:13

2

sorry you are right, the code is ok and will do the job. I looked too much at the return value of `array_map` and not at the `&entries` param of the closure. – hek2mgl Oct 21 '13 at 17:14

2

I see! array_walk would have been more correct than array_map. – Tom Macdonald Oct 21 '13 at 17:17

@ravloony yes, I think that array_walk() would being better here. – hek2mgl Oct 21 '13 at 17:18

There you are, I have fixed it. – Tom Macdonald Oct 21 '13 at 17:20

have already upvoted your answer after I got the `&$entries` usage. After all I would say using `array_walk` with a closure looks like the cleanest solution. ;) – hek2mgl Oct 21 '13 at 17:23

Glad you switched to the `array_walk()` from the map. – Orbling Oct 21 '13 at 17:31

1

Just perfect! It does exactly what I was after. – otinanai Oct 21 '13 at 18:19

hek2mgl · Answer 2 · 2013-10-21T17:01:51.473

4

There is no built in function for that. You have to write your own:

This function generalizes the problem and takes an array of glues and the data as arguments. You may refine it to fit more to your needs...

function custom_implode($glues, $pieces) {
    $result = '';
    while($piece = array_shift($pieces)) {
        $result .= $piece;
        $glue = array_shift($glues);
        if(!empty($pieces)) {
            $result .= $glue;
        }
    }

    return $result;
}

Usage:

$glues = array();
for($i = 0; $i < $end; $i++) {
    $glues []= '</li><li class="listEntry'. $i .'">';
}

echo custom_implode($glues, $data);

You can save the for loop which populates $glues if you customize the function a little bit more:

function custom_implode($start, $pieces) {
    $result = '';
    $counter = $start;
    while($piece = array_shift($pieces)) {
        $result .= $piece;
        if(!empty($pieces)) {
            $result .= '</li><li class="listEntry'. $counter .'">';
        }
    }
    return $result;
}

edited Oct 21 '13 at 17:01

answered Oct 21 '13 at 16:42

hek2mgl

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I will try this function since it's the only complete suggestion to my question. – otinanai Oct 21 '13 at 16:48
Isn't the point of `implode` to skip the verbosity of writing out the loop yourself? While this is a literal solution to your problem, it involves writing out two loops (one in your function def and one to build up your glues) and adding an extra level of complexity. – grossvogel Oct 21 '13 at 16:56
1

@grossvogel I've mentioned that. This function is more general.. Can add a special function for the OP (in order to let him just copy paste the code without need to use his brain ;) – hek2mgl Oct 21 '13 at 16:57

score 3 · Answer 3 · edited May 23 '17 at 12:14

To expand upon @ravloony's answer, you can use a mapping function with a counter to produce what you want, the following function could assist.

function implode_with_counter($glue, $array, $start, $pattern) {

    $count = $start;
    $str = "";

    array_walk($array, function($value) use ($glue, $pattern, &$str, &$count) {
        if (empty($str)) {
            $str = $value;
        } else {
            $str = $str . preg_replace('/' . preg_quote($pattern, '/') . '/', $count, $glue) . $value;
            $count++;
        }
    });

    return $str;
}

Example use:

echo implode_with_counter(' ([count]) ', range(1,5), 1, '[count]');

// Output: 1 (1) 2 (2) 3 (3) 4 (4) 5

For your case:

$entries = '<ul class="repeatData"><li class="listEntry1">'
    . implode_with_counter('</li><li class="listEntry[countme]">', $data, 2, '[countme]')
    . '</li></ul>';

Update: Alternative

An alternative approach is to just implement a callback version of implode(), and provide a function. Which is a little more universally usable, than the pattern matching.

function implode_callback($callback, array $array) {
    if (!is_callable($callback)) {
        throw InvalidArgumentException("Argument 1 must be a callable function.");
    }

    $str = "";

    $cIndex = 0;
    foreach ($array as $cKey => $cValue) {
        $str .= ($cIndex == 0 ? '' : $callback($cKey, $cValue, $cIndex)) . $cValue;
        $cIndex++;
    }

    return $str;
}

Example use:

echo implode_callback(function($cKey, $cValue, $cIndex) {
         return ' (' . $cIndex . ') ';
     }, range(1,5));

// Output: 1 (1) 2 (2) 3 (3) 4 (4) 5

Your case:

$entries = '<ul class="repeatData"><li class="listEntry1">'
    . implode_callback(function($cKey, $cValue, $cIndex) {
          return '</li><li class="listEntry' . ($cIndex + 1) . '">';
      }, $data)
    . '</li></ul>';

This is an interesting one. I was thinking of a similar answer using [`sprintf`](http://php.net/manual/en/function.sprintf.php) so the pattern could be provided with `%s` and `%d` in it for the array contents and the counter, respectively. — grossvogel, Oct 21 '13 at 17:17
@grossvogel: That would certainly be less expensive, the use of the regex replace at each implode is quite costly. It would probably be more productive to provide a simple `implode_callback()` function. I will add one. — Orbling, Oct 21 '13 at 17:22
@grossvogel: Switched it to use a `foreach` loop in the callback example, rather than the `array_walk()` as closures being used inside closures is all very well, but tends to confuse people! — Orbling, Oct 21 '13 at 17:31

score 2 · Answer 4 · answered Oct 21 '13 at 16:41

2

No, implode doesn't work that way. You will need to create your own function to do that.

answered Oct 21 '13 at 16:41

rafael.dev

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score 2 · Answer 5 · answered Oct 21 '13 at 16:45

2

You should also consider if this is what you really need. In both Javascript and CSS you can easily reference the n-th child of a node if you need to do that.

answered Oct 21 '13 at 16:45

morgoth84

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Not in this case. I'm dealing with a dynamic amount of containers and selectors are not valid in every case. – otinanai Oct 21 '13 at 16:55

PHP implode with increment value

5 Answers5