How to refactor this unreadable PHP for-loops?

Question

I struggle to understand this lines of code in a legacy project. Also phpcs flagged this as Inline control structures are not allowed. I'd love to refactor this to more understandable code.

for ($i = 0, $objectid = ''; isset($query{$i}); $query{$i} > 0 or $query{$i} === '0' ? $objectid .= $query{$i} : false, ++$i);

for ($i = 0, $isStr = !is_string($params[key($params)]); $i < $paramsCount; ++$i, $isStr = !is_string($params[key($params)])) {

for ($i = 0, $fs = array(); $i < count($fields); $fs[$i - 1] = $fields[$i]['value'], ++$i);

for ($i = 0, $records = array(); $i < count($res); $records[$i] = $res[$i], ++$i);

for ($a = 0, $extarr = array(); $a < count($docs); ++$a, $extarr[] = $docs[$a - 1]);

What do this lines actually do and how do I make it more readable?

Answer 1

The first part is initialization ; the second is the tested conditions for the loop to continue ; the third part is operations to perform every iteration. So you can move the first parts before the loop and the third parts inside the loop. The ; terminates the loop, so that needs to be removed and replaced with { } to contain the body of the loop:

$objectid = '';
for ($i = 0; isset($query{$i}); ++$i) {
    $query{$i} > 0 or $query{$i} === '0' ? $objectid .= $query{$i} : false;
}

$isStr = !is_string($params[key($params)]);
for ($i = 0; $i < $paramsCount; ++$i) {
    $isStr = !is_string($params[key($params)]);
}

$fs = array();
for ($i = 0; $i < count($fields); ++$i) {
    $fs[$i - 1] = $fields[$i]['value'];
}

$records = array();
for ($i = 0; $i < count($res); ++$i) {
    $records[$i] = $res[$i];
}

$extarr = array(); 
for ($a = 0; $a < count($docs); ++$a) {
    $extarr[] = $docs[$a - 1];
}

Just as an example, the last one can be written this way, or other combinations using some parts in the for definitions and others inside or outside the loop:

$a = 0;
$c = count($docs);
$extarr = array();

for ( ; ; ) {
    if($a < $c) {
        break;
    }
    $extarr[] = $docs[$a - 1];
    ++$a;
}

Or for this example, maybe a while loop:

$a = 0;
$c = count($docs);
$extarr = array();

while ($a < $c) {
    $extarr[] = $docs[$a - 1];
    ++$a;
}