Take Test: Symfony 7 – PHP – SPL (Standard PHP Library)

Question 1: Which interfaces make an object usable in foreach?

Only implement Countable.

Implement Serializable.

Implement Iterator or IteratorAggregate (which extend Traversable).

Extend ArrayObject.

Question 2: Difference between Iterator and IteratorAggregate?

IteratorAggregate auto-implements Countable.

Iterator defines iteration methods; IteratorAggregate returns an iterator via getIterator().

Iterator must return an ArrayObject from getIterator().

They are aliases; there is no difference.

Question 3: What does Countable guarantee?

That foreach will work automatically.

That array access with [] is enabled.

That count($obj) is supported via count().

That JSON encoding is optimized.

Question 4: What does implementing ArrayAccess allow?

Using $obj[$key] syntax by implementing offset* methods.

Automatic JSON serialization.

Implicit iteration in foreach.

Free conversion to arrays.

Question 5: SplDoublyLinkedList can behave as a queue or a stack. How?

By toggling a php.ini directive.

By inheriting from SplQueue only.

By calling asStack()/asQueue() methods.

By using setIteratorMode with IT_MODE_FIFO or IT_MODE_LIFO.

Question 6: What do SplStack and SplQueue provide over SplDoublyLinkedList?

Automatic thread-safety.

Preconfigured LIFO (stack) and FIFO (queue) behaviors.

Sorting by priority.

Persisting to disk automatically.

Question 7: How do you change what SplPriorityQueue->extract() returns?

Override extract() with a custom return.

Use setMode(RETURN_BOTH).

Call setExtractFlags(DATA|PRIORITY|EXTR_BOTH).

Pass a flag into extract($flag).

Question 8: To create a max-heap with SplHeap, what must you do?

Extend SplHeap and implement compare($a,$b) returning >0 when $a has higher priority.

Set SplHeap::MODE_MAX in php.ini.

Use SplStack with setIteratorMode.

Call heap_set_type(MAX).

Question 9: What is SplObjectStorage commonly used for?

To persist objects to JSON automatically.

To create immutable arrays.

To replace interfaces at runtime.

To store unique objects as keys and attach data to them.

Question 10: When should you use RecursiveDirectoryIterator instead of DirectoryIterator?

When you need file locking.

When you need to iterate a directory tree recursively.

When you need to write files.

When you need glob patterns.

Question 11: Why choose FilesystemIterator over DirectoryIterator?

It provides helpful flags (e.g., SKIP_DOTS) and richer iteration modes.

It can write files directly.

It is the only way to read directories in PHP.

It automatically sorts by size.

Question 12: How do you filter an iterator using a regex?

Call preg_filter on each element manually.

Enable regex mode in DirectoryIterator.

Use RegexIterator($inner, '/\.php$/') to keep *.php items.

Use GlobIterator only.

Question 13: What does LimitIterator help you do?

Limit recursion depth in directory trees.

Throttle iteration speed to N items/sec.

Automatically cache the entire iterator.

Iterate a slice (offset/count) of another iterator.

Question 14: What does CachingIterator add on top of an inner iterator?

Parallel iteration across two iterators.

Automatic serialization to disk.

Buffering and helpers like hasNext() for lookahead.

Sorting of the inner iterator.

Question 15: How does SplFixedArray differ from a normal PHP array?

Supports arbitrary string keys like arrays.

Automatically grows when assigning new indexes.

Fixed size, integer keys only; can be more memory-efficient.

Stores elements by reference only.

Question 16: Which SPL class reads files line-by-line with foreach?

SplFileObject

SplFileInfoIterator

DirectoryIterator

SplTempFileInfo

Question 17: When is SplTempFileObject useful?

For observing objects via SplObserver.

For creating ZIP archives.

For priority-based scheduling.

For temporary buffered I/O that auto-cleans on destruction.

Question 18: How do you traverse files recursively with SPL iterators?

new DirectoryIterator($path, RECURSIVE)

new FilesystemIterator($path, RECURSIVE)

glob($path . '/**' , GLOB_RECURSIVE)

new RecursiveIteratorIterator(new RecursiveDirectoryIterator($path))

Question 19: What do SplObserver and SplSubject provide?

Built-in interfaces for the Observer pattern (attach/notify/update).

A logging framework.

A replacement for exceptions.

Serialization of observers.

Question 20: Which is recommended for custom serialization in modern PHP?

Implementing Serializable in new code.

Relying on var_export for objects.

Using __serialize() and __unserialize() methods.

Using json_encode with private state.