PHP Standard Library Strategies Quiz

Why do reviewers encourage teams to lean on SPL iterators instead of rolling ad-hoc iterator classes for every collection?

What does this SplDoublyLinkedList snippet echo?

<?php
$list = new SplDoublyLinkedList();
$list->push('header');
$list->push('body');
echo $list->pop();
?>

Why would SplFixedArray be chosen for a CPU-friendly cache of 10k metrics instead of a plain PHP array?

What filenames does this DirectoryIterator loop print?

<?php
$dir = new DirectoryIterator(__DIR__ . '/templates');
foreach ($dir as $file) {
  if ($file->isFile()) {
    echo $file->getFilename() . PHP_EOL;
  }
}
?>

Why would a job scheduler reach for SplPriorityQueue when orchestrating retries?

What does this SplObjectStorage snippet echo?

<?php
$storage = new SplObjectStorage();
$a = new stdClass();
$b = new stdClass();
$storage[$a] = 'alpha';
$storage[$b] = 'beta';
$storage->detach($a);
echo $storage[$b];
?>

Why is RecursiveIteratorIterator commonly used with RecursiveDirectoryIterator in deployment tooling?

Why would SplQueue be favored for a producer-consumer worker while SplStack is saved for undo histories?

What syllables does this LimitIterator example echo?

<?php
$inner = new ArrayIterator(['alfa', 'bravo', 'charlie']);
$limit = new LimitIterator($inner, 1, 2);
foreach ($limit as $word) {
  echo substr($word, 0, 1);
}
?>

Why do file-processing daemons prefer SplFileObject over fopen/fgets pairs when tailing logs?

Why are SplMaxHeap or SplMinHeap better suited for streaming leaderboards than sorting arrays on every update?

What does this RegexIterator snippet output?

<?php
$it = new ArrayIterator(['error.log', 'readme.md', 'deploy.log']);
$regex = new RegexIterator($it, '/\.log$/');
foreach ($regex as $file) {
  echo $file . '|';
}
?>

Why do plugin systems occasionally implement SplObserver and SplSubject instead of bespoke event arrays?

Why must SplStack be rewound before reusing it in multiple foreach loops?

What does this SplPriorityQueue snippet echo?

<?php
$q = new SplPriorityQueue();
$q->insert('critical', 10);
$q->insert('minor', 1);
$q->setExtractFlags(SplPriorityQueue::EXTR_DATA);
echo $q->extract();
?>

Why does SplFixedArray::setSize help long-running daemons avoid memory creep?

Why is SplObjectStorage handy for tracking entities in memoization layers?

What does this SplQueue snippet echo?

<?php
$q = new SplQueue();
$q->enqueue('task1');
$q->enqueue('task2');
$q->dequeue();
echo $q->bottom();
?>

Why do array-like DTOs often extend ArrayObject rather than using raw arrays?

Why might CallbackFilterIterator be used in analytics pipelines instead of array_filter subsets?

Why is SplMinHeap a natural fit for top-N dashboards that need the smallest value quickly?

What does this SplFileObject snippet echo when reading a CSV line?

<?php
$file = new SplFileObject(__DIR__ . '/data/users.csv');
$file->setFlags(SplFileObject::READ_CSV);
$file->seek(1);
$record = $file->current();
echo $record[0];
?>

Why should custom SplSubject implementations always detach observers when shutting down?

Why might SplDoublyLinkedList be configured in FIFO mode when modeling queues that sometimes need random access?

Why do autoloading standards lean on spl_autoload_register rather than __autoload?

What class name does this spl_autoload_register example load?

<?php
spl_autoload_register(function ($class) {
  require __DIR__ . '/src/' . $class . '.php';
});
new Services\Mailer();
?>

Why is RecursiveDirectoryIterator often paired with filesystems that include symlink-heavy vendor trees?

Why might extension authors implement SplObserver when exposing plugin hooks?

What does this ArrayObject snippet echo after appending?

<?php
$list = new ArrayObject(['alpha']);
$list->append('beta');
$it = $list->getIterator();
foreach ($it as $value) {
  $last = $value;
}
echo $last;
?>

Why do data-merging jobs use MultipleIterator when combining price feeds from separate iterators?

Why does SplPriorityQueue extract elements in heap order even if you iterate with foreach?

Why might SplFixedArray be converted to a regular array before passing data to json_encode?

What does this SplMinHeap snippet echo?

<?php
$heap = new SplMinHeap();
$heap->insert(5);
$heap->insert(2);
$heap->insert(9);
echo $heap->extract();
?>

Why is SplObjectStorage valuable for access-control layers that need to track permissions per object instance?

Why do asset pipelines inspect SplFileInfo objects before copying binaries?