PHP implode with increment value - php

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.

Answer 1

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.

Answer 2

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;
}

Answer 3

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>';

Answer 4

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

Answer 5

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.