Iterators in PHP 5 Dr Tarique Sani CTO, SANIsoft Nagpur, India

Dr Tarique Sani

CTO, SANIsoft

Nagpur, India

Who am I? A PHP programmer since 5+ years Author of PHP projects like Coppermine, PHPlib and WAPpop CTO, of my own software development company working exclusively with PHP ...

A PHP programmer since 5+ years

Author of PHP projects like Coppermine, PHPlib and WAPpop

CTO, of my own software development company working exclusively with PHP

...

Who are you? Who has been working with PHP Who is familiar with some OOP concepts Who wants to learn more about new features offered by PHP 5 – specially Iterators

Who has been working with PHP

Who is familiar with some OOP concepts

Who wants to learn more about new features offered by PHP 5 – specially Iterators

Introduction to Iterators PHP projects perpetually re-inventing the wheel Standardising some of the wheels – good idea Reusable code Same map for developers SPL (Standard PHP Library) by Marcus Boerger "is a collection of interfaces” part of the core distribution of PHP5 On by default SPL for now has interfaces for Iterators

PHP projects perpetually re-inventing the wheel

Standardising some of the wheels – good idea

Reusable code

Same map for developers

SPL (Standard PHP Library) by Marcus Boerger

"is a collection of interfaces”

part of the core distribution of PHP5

On by default

SPL for now has interfaces for Iterators

So what is an Iterator? A design pattern Intent of an iterator "provide an object which traverses some aggregate structure, abstracting away assumptions about the implementation of that structure." !! ???

A design pattern

Intent of an iterator

"provide an object which traverses some aggregate structure, abstracting away assumptions about the implementation of that structure."

Some common PHP code Loop through a MySQL query // Fetch the "aggregate structure" $result = mysql_query(" SELECT user,pass FROM auth" ); // Iterate over the structure while ( $row = mysql_fetch_array($result) ) { // do stuff with the row here }

Some common PHP code To read the contents of a array: // Fetch the "aggregate structure" $array = ; //Whatever it takes foreach ($array as $key => $value) { // iterate through array elements }

Some common PHP code To read the contents of a file // Fetch the "aggregate structure" $fp = fopen("/home/tarique/log.txt", "r"); // Iterate over the structure while (!feof($fp)) { $line = fgets($fp); // do stuff with the line here }

Some common PHP code To read the contents of a directory: // Fetch the "aggregate structure" $dir = opendir('/home/tarique/files'); // Iterate over the structure while ( $file = readdir($dir) ) { print "$file
"; }

Bugs!!! File named '0' in the directory Solution - while (false != = ($file = readdir($dir))) { print "$file
"; } Cumbersome.... Is there an easier solution?

File named '0' in the directory

Solution -

Cumbersome....

Is there an easier solution?

Yes! DirectoryIterator Same result is achieved by foreach (new DirectoryIterator($path) as $file) { print "$file
"; } Shorter code Cleaner code Safer code (can't forget === )

Same result is achieved by

Shorter code

Cleaner code

Safer code (can't forget === )

More features of SPL / Iterators Both standalone iterators and iterators meant to be chained using the 'FilterIterator' in conjunction with a 'DirectoryIterator' 'LimitIterator' allows you to 'page' through an iterator's results You can create your own Iterators in PHP For looping through IMAP results, Thumbnails in a gallery, SQL result sets

Both standalone iterators and iterators meant to be chained

using the 'FilterIterator' in conjunction with a 'DirectoryIterator'

'LimitIterator' allows you to 'page' through an iterator's results

You can create your own Iterators in PHP

For looping through IMAP results, Thumbnails in a gallery, SQL result sets

More of DirectoryIterator Still not good returning . and .. returning directories Solution isDir( ) $dir = new DirectoryIterator( '/www/www.example.com/'); foreach ($dir as $file) { print "$file
"; } . .. email.html images includes index.html search.html

Still not good

returning . and ..

returning directories

Solution

isDir( )

More of DirectoryIterator Still not good returning . and .. returning directories Solution isDir( ) $dir = new DirectoryIterator( '/www/www.example.com/'); foreach ($dir as $file) { if (! $file->isDir( )) { print "$file
"; } } email.html index.html search.html

Still not good

returning . and ..

returning directories

Solution

isDir( )

DirectoryIterator Methods getPath( ) Returns the opened path (e.g., /home/tarique/public_html) getFilename( ) Returns the current filename (e.g., index.html) getPathname( ) Returns the current path and file isDir( ) Determines whether the current file is a directory isDot( ) Determines whether the current file is a dot file

getPath( )

Returns the opened path (e.g., /home/tarique/public_html)

getFilename( )

Returns the current filename (e.g., index.html)

getPathname( )

Returns the current path and file

isDir( )

Determines whether the current file is a directory

isDot( )

Determines whether the current file is a dot file

Cut the classroom crap!! Show us something useful!!

Time for me to....

Create your own Iterator Overview of the Iterator 'Interface' and methods See how PHP 5 handles multiple queries Create a custom Iterator to handle multiple queries

Overview of the Iterator 'Interface' and methods

See how PHP 5 handles multiple queries

Create a custom Iterator to handle multiple queries

Implementing the Iterator Interface The Iterator interface is a set of 5 methods rewind( ) - Resets iterator list to its start valid( ) - Says if there are additional items left in the list next( ) - Moves iterator to the next item in the list key( ) - Returns the key of the current item current( ) - Returns the current item

The Iterator interface is a set of 5 methods

rewind( ) - Resets iterator list to its start

valid( ) - Says if there are additional items left in the list

next( ) - Moves iterator to the next item in the list

key( ) - Returns the key of the current item

current( ) - Returns the current item

So you can change this... Involves four functions and a do/while loop if (mysqli_multi_query($db, $query)) { do { if ($result = mysqli_store_result($db)) { while ($row = mysqli_fetch_row($result)) { print "$row[0]
"; } mysqli_free_result($result); } } while (mysqli_next_result($db)); }

Involves four functions and a do/while loop

to this..... much simpler and cleaner foreach (new MySQLiQueryIterator($db, $query) as $result) { if ($result) { while ($row = mysqli_fetch_row($result)) { print "$row[0]
"; } } }

much simpler and cleaner

MySQL multi-query iterator Set some of the needed variables Constructor assigns the $link and $query to class variables class MySQLiQueryIterator implements Iterator { protected $link; protected $query; protected $key; protected $valid; protected $result; //Constructor public function __construct($link, $query) { $this->link = $link; $this->query = $query; }

Set some of the needed variables

Constructor assigns the $link and $query to class variables

multi-query iterator – rewind( ) Sets the key to 0 Executes the query and store the result else make valid false public function rewind( ) { $this->key = 0; if (mysqli_multi_query($this->link, $this->query)) { $this->result = mysqli_store_result($this->link); $this->valid = true; } else { $this->result = false; $this->valid = false; } }

Sets the key to 0

Executes the query and store the result else make valid false

multi-query iterator – valid( ) Returns the result from mysqli_more_results( ) Catch the current result to be returned not the next public function valid( ) { // mysqli_more_results( ) is one ahead of Iterator valid( ) $valid = $this->valid; $this->valid = mysqli_more_results($this->link); return $valid; }

Returns the result from mysqli_more_results( )

Catch the current result to be returned not the next

multi-query iterator – key( ) public function key( ) { return $this->key; }

multi-query iterator – current( ) public function current( ) { return $this->result; }

multi-query iterator - next() Frees result, increments key Fetches an additional row using mysqli_store_result( ) public function next( ) { if ($this->result) { mysqli_free_result($this->result); } $this->key++; if (mysqli_next_result($this->link)) { $this->result = mysqli_store_result($this->link); } else { $this->result = false; } }

Frees result, increments key

Fetches an additional row using mysqli_store_result( )

multi-query iterator - Usage Worth the trouble Use in code simplified $db = mysqli_connect('db.example.org'); $query = >>>_SQL_ DROP TABLE IF EXISTS users; CREATE TABLE users(username VARCHAR(50) UNIQUE, password VARCHAR(50)); INSERT INTO users VALUES('tarique', '123456'); INSERT INTO users VALUES('aasim', 'abcdef'); SELECT username FROM users; _SQL_;

Worth the trouble

Use in code simplified

multi-query iterator - Usage foreach (new MySQLiQueryIterator($db, $query) as $result) { if ($result) { while ($row = mysqli_fetch_row($result)) { print "$row[0]
"; } } } tarique aasim

Is that it?

Chaining Iterators FilterIterator abstract class You must define accept( ) method LimitIterator behaves just like the SQL LIMIT

FilterIterator

abstract class

You must define accept( ) method

LimitIterator

behaves just like the SQL LIMIT

FilterIterator - Example Takes 2 arguments in constructor – an Iterator and regex accept( ) returns true if the regex matches class RegexFilter extends FilterIterator { protected $regex; public function _ _construct(Iterator $it, $regex) { parent::_ _construct($it); $this->regex = $regex; } public function accept( ) { return preg_match($this->regex, $this->current( )); } }

Takes 2 arguments in constructor – an Iterator and regex

accept( ) returns true if the regex matches

FilterIterator - Example Takes 2 arguments in constructor – an Iterator and regex accept( ) returns true if the regex matches $dir = new DirectoryIterator('/www/www.example.com/') { $filtered_dir = new RegexFilter($dir, '/html$/i'); foreach ($filtered_dir as $file); print "$file
"; } thumb.html index.html display.html

Takes 2 arguments in constructor – an Iterator and regex

accept( ) returns true if the regex matches

LimitIterator - Example Can be directly instantiated Takes an Iterator, start position and number of items to return foreach(new LimitIterator( new DirectoryIterator('/www/www.example.com/'), 2, 2) as $file) { print "$file
"; } index.html images

Can be directly instantiated

Takes an Iterator, start position and number of items to return

Combined - Example return the first file with html extension foreach(new LimitIterator(new RegexFilter( new DirectoryIterator('/www/www.example.com/'), '/html$/i'), 0, 1) as $file) { print "$file
"; } index.html

return the first file with html extension

Is that it...

SimpleXML Iterator Takes and XML string and makes it an iterable object Combine it with a LimitIterator and you can page the XML results $ab = file_get_contents('address-book.xml'); $page = 0; $limit = 10; foreach (new LimitIterator(new SimpleXMLIterator($ab), $page * $limit, $limit) as $person) { print "$person->firstname $person->lastname: $person->email
"; }

Takes and XML string and makes it an iterable object

Combine it with a LimitIterator and you can page the XML results

RecursiveIterator Interface RecursiveIterator interface extends the existing Iterator interface Two additional methods: hasChildren( ) getChildren( ) These methods are used to navigate through sublists.

RecursiveIterator interface extends the existing Iterator interface

Two additional methods:

hasChildren( )

getChildren( ) These methods are used to navigate through sublists.

RecursiveDirectoryIterator RecursiveIteratorIterator. This class is an Iterator for classes that implement the RecursiveIterator interface $dir = new RecursiveIteratorIterator( new RecursiveDirectoryIterator('/www/www.example.com'), true); foreach ($dir as $file) { print $file->getPathname( ) . "
"; } /www/www.example.com/email.html /www/www.example.com/images /www/www.example.com/images/logo.gif

RecursiveIteratorIterator. This class is an Iterator for classes that implement the RecursiveIterator interface

Is that it!!! @#$W**

Yes and No Lots of other iterators built in http://in.php.net/spl Sources in the ext/spl/examples

Lots of other iterators built in

http://in.php.net/spl

Sources in the ext/spl/examples