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New SPL Features in PHP 5.3
Matthew Turland
TEK-X
May 20, 2010
Hi! My name is…
• Senior Platform Engineer for Synacor, Inc.
• Former author and TE for php|architect
• Author of Web Scraping with PHP
• Past contributor to Zend Framework
• Lead developer of Phergie
• ULL alumni with a BS in computer science
And I work for…
• Provides internet solutions to ISPs, media companies, and advertisers
• International company with offices in Buffalo, New York City, Los Angeles, and Amsterdam
• Clientele includes most of the top 20 cable providers in the United States
• Great company – join us!
What about you?
• Used the SPL before?
• Using PHP 5.3?
• Computer science background?
• Knowledge of data structures?
Pre-5.3 SPL Features
• Classes: ArrayObject, SplFileInfo, SplSubject, SplObserver, etc.
• Iterators: RecursiveIteratorIterator, FilterIterator, LimitIterator, etc.
• Interfaces: ArrayAccess, Countable, Iterator, IteratorAggregate, etc.
• Functions: spl_autoload_register, iterator_to_array, spl_object_hash, etc.
Containers
“A container is a class, a data structure, or
an abstract data type whose instances are
collections of other objects. They are used
to store objects in an organized way
following specific access rules.”
Container (data structure) - Wikipedia
Why containers?
• We already have arrays and strings!
array() 'string'
Two excellent reasons
• Versus traditional arrays, there is potential for:
– Less CPU usage
– Less memory usage
Arrays are (not always) great
• Flexible general purpose container
• Underlying hash table algorithm is not always ideal for the task at hand
Warning: Benchmarks Ahead
• Lies, Outrageous Lies, and Benchmarks
• PHP 5.3.2 compiled on Ubuntu 9.10
• Intel Core2Duo 1.83 GHz, 4 GB DDR2 RAM
• Performance results are shown in executions per second rather than time per execution to avoid really small numbers
• Code and results
The List
SplFixedArray - What
• Like an array, but with a fixed length
• Only allows integers >= 0 for keys
• Can be resized, but at a cost
• Not compatible with array functions
SplFixedArray - When
• It’s best to use this when:
– You know in advance how many elements you want to store (e.g. mysql_num_rows)
– You only need to access elements in sequential order
SplFixedArray - Code
<?php
$a = array();
for ($i = 0; $i < $argv[1]; $i++) {
$a[$i] = $i;
$i = $a[$i];
}
<?php
$a = new SplFixedArray($argv[1]);
for ($i = 0; $i < $argv[1]; $i++) {
$a[$i] = $i;
$i = $a[$i];
}
SplFixedArray - EPS
SplFixedArray - Memory
SplDoublyLinkedList - What
• Mainly intended as a parent class
• Same unlimited size as arrays without the associated hash map algorithm
• Less performance, but more memory efficiency
SplDoublyLinkedList - When
• It’s best to use this when:
– You do not know in advance how many elements you want to store
– You only need to access elements in sequential order
SplDoublyLinkedList - Code
<?php
$a = array();
for ($i = 0; $i < $argv[1]; $i++) {
$a[] = $i;
$i = $a[$i];
}
<?php
$a = new SplDoublyLinkedList($argv[1]);
for ($i = 0; $i < $argv[1]; $i++) {
$a[] = $i;
$i = $a[$i];
}
SplDoublyLinkedList - EPS
SplDoublyLinkedList - Memory
The Stack
SplStack - What
• 2 operations
– Push: [] for both array and SplStack
– Pop: array_pop() vs SplStack::pop()
• Last In, First Out (LIFO)
– The last item pushed onto the top of the stack is the first item that will be popped off of the top of the stack
SplStack - When
• It’s best to use this when:
– You do not know in advance how many elements you want to store
– You only ever need to access the last element you stored
SplStack - Code
<?php
$a = array();
for($i = 0; $i < $argv[1]; $i++) {
$a[] = $i;
}
for($i = 0; $i < $argv[1]; $i++) {
array_pop($a);
}
SplStack - Code (cont.)
<?php
$a = new SplStack;
for($i = 0; $i < $argv[1]; $i++) {
$a[] = $i;
}
for($i = 0; $i < $argv[1]; $i++) {
$a->pop();
}
SplStack - EPS
SplStack - Memory
The Queue
SplQueue - What
• 2 operations
– Enqueue: [] for both array and SplQueue
– Dequeue: array_shift() vs SplQueue::dequeue()
• First In, First Out (FIFO)
– The first item added to the end of the queue will be the first item removed from the front of the queue
SplQueue - When
• It’s best to use this when:
– You do not know in advance how many elements you want to store
– You only ever need to access the remaining element that was stored earliest
SplQueue - Code
<?php
$a = array();
for($i = 0; $i < $argv[1]; $i++) {
$a[] = $i;
}
for($i = 0; $i < $argv[1]; $i++) {
array_shift($a);
}
SplQueue - Code (cont.)
<?php
$a = new SplQueue;
for($i = 0; $i < $argv[1]; $i++) {
$a[] = $i;
}
for($i = 0; $i < $argv[1]; $i++) {
$a->dequeue();
}
SplQueue - EPS
SplQueue - Memory
The Heap
SplHeap - What
• 2 operations
– Insert: [] + sort vs SplHeap::insert()
– Remove: array_shift() vs SplHeap::extract()
• Internally reorders items based on comparison
– SplHeap::compare() can be overridden
• Subclasses
– SplMinHeap
– SplMaxHeap
• Better worst-case scenario performance versus arrays (heap sort versus quick sort)
SplHeap - When
• It’s best to use this when:
– You do not know in advance how many elements you want to store
– You need to access elements in an order based on how they compare to each other
SplMinHeap - Code
<?php
$a = array();
for($i = 0; $i < $argv[1]; $i++) {
$a[] = rand(1, $argv[1]);
sort($a);
}
for($i = 0; $i < $argv[1]; $i++) {
array_shift($a);
}
SplMinHeap - Code (cont.)
<?php
$a = new SplMinHeap;
for($i = 0; $i < $argv[1]; $i++) {
$a->insert(rand(1, $argv[1]));
}
for($i = 0; $i < $argv[1]; $i++) {
$a->extract();
}
SplMinHeap - EPS
SplMinHeap - Memory
The Priority Queue
SplPriorityQueue - What
• Accepts a priority with the element value
• Element with highest priority comes out first
• Priorities may be of any comparable type
• SplPriorityQueue::compare() can be overridden
• Operates similarly to a heap
– In fact, it uses a heap internally for storage
SplPriorityQueue - When
• It’s best to use this when:
– You do not know in advance how many elements you want to store
– You need to access elements in an order based on how priority values associated with those elements compare to each other
SplPriorityQueue - Code<?php
$threshold = $argv[1] * 0.1;
$a = array();
$i = 0;
do {
if ($i <= $argv[1]) {
$a[] = array($i, rand(1, 10));
usort($a, 'priority_sort');
}
if ($i > $threshold) {
array_shift($a);
}
$i++;
} while (count($a));
function priority_sort($a, $b) {
return $a[1] - $b[1];
}
SplPriorityQueue - Code (cont.)<?php
$threshold = $argv[1] * 0.1;
$a = new SplPriorityQueue;
$i = 0;
do {
if ($i < 1) {
$a->insert($i, rand(1,10));
}
if ($i > $threshold) {
$a->extract();
}
$i++;
} while (count($a));
SplPriorityQueue - EPS
SplPriorityQueue - Memory
The Set
The Composite Hash Map
Just pretend the red pills are objects.
SplObjectStorage - What
• Combination of two data structures
– Composite hash map: a hash map with objects for keys; the spl_object_hash() function must be used for arrays to have this capability
– Set: focuses on a group of values rather than individual values with operations like union, intersection, difference, and element_of; no concept of sequential order
• Currently lacks a method for the intersection operation
SplObjectStorage - When
• It’s best to use this when:
– You need to store data using composite (i.e. non-scalar) keys
– You need the ability to access data using set operations more so than accessing it in a particular order
SplObjectStorage - Code<?php
$a = array();
for ($i = 0; $i < $argv[1]; $i++) {
$object = new stdClass;
$a[spl_object_hash($object)] = $object;
}
$a = array();
$b = array();
for ($i = 0; $i < $argv[1]; $i++) {
$a[] = rand(1, $argv[1]);
$b[] = rand(1, $argv[1]);
}
$c = array_merge($a, $b);
$c = array_diff($a, $b);
SplObjectStorage - Code (cont.)<?php
$a = new SplObjectStorage;
for ($i = 0; $i < $argv[1]; $i++) {
$object = new stdClass;
$a->attach($object, $object);
}
$a = new SplObjectStorage;
$b = new SplObjectStorage;
for ($i = 0; $i < $argv[1]; $i++) {
$a->attach((object) rand(1, $argv[1]));
$b->attach((object) rand(1, $argv[1]));
}
$c = clone $a;
$c->addAll($b);
$c = clone $a;
$c->removeAll($b);
SplObjectStorage - EPS
SplObjectStorage - Memory
Thank this guy
• Etienne Kneuss did a lot of the work on the new SPL features in PHP 5.3
Some great SPL resources
• SPL in the PHP manual
• Etienne Kneuss' blog
• "SPL to the Rescue" by Elizabeth Smith
• “SPL, a bridge not too far” by Michelangelo van Dam
• This presentation as a blog post
Possible future SPL features
• Graphs
– Contain nodes and edges connecting them
– Directional / non-directional
– Cyclic / acyclic
– Connected / unconnected
– Edge costs
• Trees
– Acyclic unidirectional graph
– Hierarchical in nature
That’s all, folks
• Any questions?
• http://synacor.com
• http://matthewturland.com
• @elazar on Twitter
• Elazar on the Freenode IRC network
