SPL: The Missing Link in Development

The Standard PHP Library (SPL) is the php extension that so many developers pass on out of lack of knowledge, NO MORE! Jake Smith will introduce you to the benefits of utilizing SPL features (iterators, interfaces, exceptions and autoloader). Also, continuing from last months talk he will introduce some new PHP 5.3 SPL classes.

Transcript

1. SPL: The Missing Link in Development
   Jake Smith
   Dallas PHP - 7/13/2010
   

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2. What is SPL?
   • A  library  of  standard  interfaces,  classes,  
   and  functions  designed  to  solve  common  
   programming  problems  and  allow  engine  
   overloading.
   Definition Source: http://elizabethmariesmith.com/
   

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3. SPL Background
   • Provides Interfaces, Classes and Functions
   • As of PHP 5.3 you can not turn off SPL
   • Poor documentation root of poor
   adoption.
   

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4. SPL Autoloading
   

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5. Before SPL Autoload
   set_include_path(dirname(__FILE__) . '/lib' . PATH_SEPARATOR . get_include_path());
   function __autoload($class_name) {
   $path = dirname(__FILE__) . '/lib/' . str_replace('_', '/', strtolower
   ($class_name)) . '.php';
   if (file_exists($path)) {
   require $path;
   } else {
   die('Class ' . $path . ' Not Found');
   }
   }
   class Form_Element_Text extends Form_Element
   {
   public function __construct($name = '', $attrs = array())
   {
   $this->_name = $name;
   $this->_attrs = $attrs;
   }
   Class Name
   

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6. Autoloading w/SPL
   /*** nullify any existing autoloads ***/
   spl_autoload_register(null, false);
   /*** specify extensions that may be loaded ***/
   spl_autoload_extensions('.php, .class.php');
   /*** class Loader ***/
   function classLoader($class)
   {
   $filename = strtolower($class) . '.class.php';
   $file ='classes/' . $filename;
   if (!file_exists($file))
   {
   return false;
   }
   include $file;
   }
   /*** register the loader functions ***/
   spl_autoload_register('classLoader');
   Example Source: http://www.phpro.org/tutorials/SPL-Autoload.html
   

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7. Multiple Autoloaders
   /*** nullify any existing autoloads ***/
   spl_autoload_register(null, false);
   spl_autoload_register(array('Doctrine_Core', 'autoload'));
   spl_autoload_register(array('Doctrine_Core', 'modelsAutoload'));
   

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8. Multiple Autoloaders
   class Doctrine_Core
   {
   public static function autoload($className)
   {
   if (strpos($className, 'sfYaml') === 0) {
   require dirname(__FILE__) . '/Parser/sfYaml/' . $className . '.php';
   return true;
   }
   if (0 !== stripos($className, 'Doctrine_') || class_exists($className, false) || interface_exists($className, false)) {
   return false;
   }
   $class = self::getPath() . DIRECTORY_SEPARATOR . str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';
   if (file_exists($class)) {
   require $class;
   return true;
   }
   return false;
   }
   

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9. SPL Functions
   

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10. iterator_to_array
    • Takes an iterator object, an object that
    implements Traversable
    • All iterators implement Traversable
    

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11. spl_object_hash
    • MD5 hash of internal pointer
    • When objects are destroyed their object
    hash is released
    • Object Hash ID can/will be reused after
    destruction.
    

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12. SPL Classes
    • ArrayObject
    • SplFileInfo
    

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13. ArrayObject
    • Allows objects to act like arrays
    • Does not allow usage of array functions on
    object
    • Built in methods: ksort, usort, asort,
    getArrayCopy
    

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14. SplFileInfo
    • Object that returns information on Files/
    Folders
    • isDir, isFile, isReadable, isWritable, getPerms
    (returns int), etc.
    Example Source: http://us3.php.net/manual/en/class.splfileinfo.php
    

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15. SPL Interfaces
    • ArrayAccess
    • Iterator
    • RecursiveIterator
    • Countable
    • SeekableIterator
    • SplSubject/SplObserver
    

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16. Observer Pattern (SPL)
    • Great for applying hooks
    • Exception Handling
    • User Authentication
    

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17. SplSubject
    class ExceptionHandler implements SplSubject
    {
    private $_observers = array();
    public function attach(SplObserver $observer)
    {
    $id = spl_object_hash($observer);
    $this->_observers[$id] = $observer;
    }
    public function detach(SplObserver $observer)
    {
    $id = spl_object_hash($observer);
    unset($this->_observers[$id]);
    }
    public function notify()
    {
    foreach($this->_observers as $obs) {
    $obs->update($this);
    }
    }
    public function handle(Exception $e)
    {
    $this->exception = $e;
    $this->notify();
    }
    }
    Example Source: http://devzone.zend.com/article/12229
    

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18. SplObserver
    Class Mailer implements SplObserver {
    public function update(SplSubject $subject)
    {
    // Do something with subject object
    }
    }
    // Create the ExceptionHandler
    $handler = new ExceptionHandler();
    // Attach an Exception Logger and Mailer
    $handler->attach(new Mailer());
    // Set ExceptionHandler::handle() as the default
    set_exception_handler(array($handler, 'handle'));
    Example Source: http://devzone.zend.com/article/12229
    

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19. ArrayAccess
    • OffsetExists - Values exists for key, returns
    boolean
    • OffsetSet - Set value for key
    • OffsetGet - Return value for key
    • OffsetUnset - Remove value from array
    • Note that if the array is numerically indexed, a call to array_values() will be required to re-index
    the array if that is the behaviour required.
    Example Source: http://www.phpro.org/tutorials/Introduction-to-SPL-ArrayAccess.html
    

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20. ArrayAccess Example
    class book implements ArrayAccess
    {
    public $title;
    public $author;
    public $isbn;
    public function offsetExists( $offset )
    {
    return isset( $this->$offset );
    }
    public function offsetSet( $offset, $value)
    {
    $this->$offset = $value;
    }
    public function offsetGet( $offset )
    {
    return $this->$offset;
    }
    public function offsetUnset( $offset )
    {
    unset( $this->$offset );
    }
    }
    Example Source: http://www.phpro.org/tutorials/Introduction-to-SPL-ArrayAccess.html
    

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21. Iterator
    • Provides basic iterator functionality
    (foreach)
    • Interface requires the following methods
    • current(), key(), next(), rewind(), valid()
    

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22. Recursive Iterator
    • A foreach only goes top level, but many
    times you need to dig deeper
    • Recursive Iterator extends Iterator and
    requires hasChildren() and getChildren()
    

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23. Countable
    • Internal Counter
    class loopy
    {
    public function count()
    {
    static $count = 0;
    return $count++;
    }
    public function access()
    {
    $this->count();
    // Method logic
    }
    }
    

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24. SeekableIterator
    • Other iterators must start at beginning of
    an array, but seekable allows you to change
    iteration start point.
    class PartyMemberIterator implements SeekableIterator
    {
    public function seek($index)
    {
    $this->rewind();
    $position = 0;
    while ($position < $index && $this->valid()) {
    $this->next();
    $position++;
    }
    if (!$this->valid()) {
    throw new OutOfBoundsException('Invalid position');
    }
    }
    Example Source: http://devzone.zend.com/article/2565
    

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25. SPL Iterators
    • ArrayIterator
    • LimitIterator
    • DirectoryIterator
    • RecursiveDirectoryIterator
    • GlobIterator
    

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26. ArrayIterator
    • Implements: Iterator, Traversable,
    ArrayAccess, SeekableIterator, Countable
    • Used to Iterate over ArrayObject or PHP
    array
    

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27. ArrayIterator
    // Using While
    /*** create a new object ***/
    $object = new ArrayIterator($array);
    /*** rewind to the beginning of the array ***/
    $object->rewind();
    /*** check for valid member ***/
    while($object->valid())
    {
    /*** echo the key and current value ***/
    echo $object->key().' -> '.$object->current().'
    ';
    /*** hop to the next array member ***/
    $object->next();
    }
    // Using Foreach
    $object = new ArrayIterator($array);
    foreach($object as $key=>$value)
    {
    echo $key.' => '.$value.'
    ';
    }
    Example Source: http://www.phpro.org/tutorials/Introduction-to-SPL.html#6
    

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28. LimitIterator
    • Used similar to Limit in SQL
    // Show 10 files/folders starting from the 3rd.
    $offset = 3;
    $limit = 10;
    $filepath = '/var/www/vhosts/mysite/images'
    $it = new LimitIterator(new DirectoryIterator($filepath), $offset, $limit);
    foreach($it as $r)
    {
    // output the key and current array value
    echo $it->key().' -- '.$it->current().'
    ';
    }
    

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29. DirectoryIterator
    • If you’re accessing the filesystem this is the
    iterator for you!
    • Returns SplFileInfo object
    

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30. DirectoryIterator
    $hdl = opendir('./');
    while ($dirEntry = readdir($hdl))
    {
    if (substr($dirEntry, 0, 1) != '.')
    {
    if(!is_file($dirEntry))
    {
    continue;
    }
    $listing[] = $dirEntry;
    }
    }
    closedir($hdl);
    foreach($listing as $my_file)
    {
    echo $my_file.'
    ';
    }
    try
    {
    /*** class create new DirectoryIterator Object ***/
    foreach ( new DirectoryIterator('./') as $Item )
    {
    echo $Item.'
    ';
    }
    }
    /*** if an exception is thrown, catch it here ***/
    catch(Exception $e)
    {
    echo 'No files Found!
    ';
    }
    

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31. RecursiveDirectory
    Iterator
    • Move out of the top level and get all
    children files/folders
    $dir = '/Users/jsmith/Sites/vhosts/test.local/wwwroot';
    $iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($dir));
    // could use CHILD_FIRST if you so wish
    foreach ($iterator as $file) {
    echo $file . "
    ";
    }
    

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32. GlobIterator (5.3)
    • Very Similar to DirectoryIterator
    • Only use if you want to convert old glob
    code into an iterator object
    • returns SplFileInfo Objects
    

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33. SPL Exceptions
    • Logic Exception
    • BadFunction
    • BadMethodCall
    • InvalidArgument
    • OutOfRange
    • RuntimeException
    • OutOfBounds
    • Range
    • UnexpectedValue
    • Underflow
    Example Source: http://www.php.net/manual/en/spl.exceptions.php
    

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34. New SPL in PHP 5.3
    

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35. SplFixedArray
    • Array with pre-defined dimensions
    • Shows great speed for setting and
    retrieving
    • If you change Array dimensions, it will
    crawl.
    

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36. SplHeap
    • Automatically reorder after insert, based
    off of compare() method
    • Extract is similar to array_shift()
    • Great memory usage!
    Example Source: http://www.slideshare.net/tobias382/new-spl-features-in-php-53
    

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37. SplMaxHeap
    • Subclass of SplHeap
    • When you extract() a value it will return in
    order from greatest to least
    $heap = new SplMaxHeap();
    $heap->insert('b');
    $heap->insert('a');
    $heap->insert('c');
    echo $heap->extract()."\n";
    echo $heap->extract()."\n";
    echo $heap->extract()."\n";
    // OUTPUT:
    // c
    // b
    // a
    Example Source: http://www.alberton.info/php_5.3_spl_data_structures.html
    

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38. SplMinHeap
    • Subclass of SplHeap
    • When you extract() a value it will return in
    order from least to greatest
    $heap = new SplMinHeap();
    $heap->insert('b');
    $heap->insert('a');
    $heap->insert('c');
    echo $heap->extract()."\n";
    echo $heap->extract()."\n";
    echo $heap->extract()."\n";
    // OUTPUT:
    // a
    // b
    // c
    Example Source: http://www.alberton.info/php_5.3_spl_data_structures.html
    

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39. SplDoublyLinkedList
    • Do not know size of list/array
    • Can only be read sequentially
    • Less processing power required, on large
    data sets provides better memory usage
    

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40. SplStack
    • Method: push and pop
    • LIFO
    

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41. SplQueue
    • Methods: enqueue and dequeue
    • FIFO
    

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42. Questions?
    

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43. Useful Links
    • SPL in 5.3
    • http://www.alberton.info/
    php_5.3_spl_data_structures.html
    • http://www.slideshare.net/tobias382/new-spl-features-in-
    php-53
    • Intro to SPL
    • http://www.phpro.org/tutorials/Introduction-to-SPL.html
    • http://www.slideshare.net/DragonBe/spl-not-a-bridge-too-
    far
    

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44. Thanks for listening!
    Contact Information
    [t]: @jakefolio
    [e]: jake@dallasphp.org
    [w]: http://www.jakefolio.com
    [irc]: #dallasphp
    

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