Martin Kruliš 19. 3. 2015 by Martin Kruliš (v1.0)1

by Martin Kruliš (v1.0) 1

Files and FilesystemMartin Kruliš

19. 3. 2015

by Martin Kruliš (v1.0) 2

Low Level C-like API◦ fopen(), fread(), fwrite(), fclose(), …◦ Data are treated as strings

Note that per-byte processing is extremely slow

File-wide Operations◦ fpassthru(), readfile() – whole file is spilled to

the output◦ file_get_contents(), file_put_contents()

Read/write the entire file to/from a string◦ file() – reads entire file as an array of lines

19. 3. 2015

Working with Files

by Martin Kruliš (v1.0) 3

POSIX Based API◦ Only partial functionality on non-POSIX OSes◦ touch() – sets current time to a file◦ tmpfile() – creates temporary file◦ rename(), unlink() – unlink ~ delete◦ mkdir(), rmdir() – make/remove dir

Synchronization Issues◦ POSIX atomic operations (append, mkdir, …)◦ Advisory file locking mechanism – flock()

Locks are bounded to processes, multi-threaded web server need not guarantee sync. between PHP scripts

19. 3. 2015

File System

by Martin Kruliš (v1.0) 4

File Properties (Size, Type, Creation Time, …)◦ Dedicated functions for some properties

filesize(), filetype(), filectime()◦ Reading all properties at once

stat(), lstat(), fstat()

POSIX Access Rights (rwx)◦ Testing functions

is_file(), is_readable(), is_writeable(), …◦ Modification of rights and owner

chmod(), chown(), chgrp()

19. 3. 2015

File Properties and Rights

by Martin Kruliš (v1.0) 5

Traversing Directories◦ Iterative – opendir(), readdir(), closedir()◦ scandir() – returns array with directory contents◦ dir() – returns object of Directory class

Directory Paths◦ glob() – expanding wildcards◦ dirname(), basename() – get part of path◦ pathinfo() – parses path and return components◦ realpath() – converts symbolic to real path

Absolute path without links, ./, and ../

19. 3. 2015

Directories and Paths

by Martin Kruliš (v1.0) 6

CSV Files◦ Comma (semicolon) separated values◦ API uses file handlers from fopen()

fgetcsv() – reads one CSV line fputcsv() – writes one CSV line

INI Files◦ Configuration files with “name = value” items◦ parse_ini_file() – reads the entire file and

yields an associative array Optionally divides the data to sections

19. 3. 2015

Formatted Files

by Martin Kruliš (v1.0) 7

ZIP Files (*.zip)◦ Rather complicated (ZIP is multi-file container)◦ Represented by ZipArchive class

Zlib – gzip library (*.gz)◦ Similar functions to standard C-like API

gzopen(), gzread(), gzwrite(), gzclose(), … BZip Library (*.bz2)

◦ Similar to Zlib (bzopen(), …) Other libraries are available (RAR, LZF, …)

◦ TAR only as PECL extension

19. 3. 2015

Compression

by Martin Kruliš (v1.0) 8

XML and JSONMartin Kruliš

19. 3. 2015

When confronted with a problem, some people thinks: “Hey, I’ll use

XML!”Then they have two problems…

by Martin Kruliš (v1.0) 9

Parsing Process◦ Loading XML from text file into memory structures

Simple API for XML (SAX)◦ The document is processed sequentially◦ Important “events” are reported to the user

Opening/closing an element, attribute found, … Document Object Model (DOM)

◦ Tree-based structure with object oriented API◦ Nodes of the tree represent elements, attributes,

text content, ….◦ More suitable for mutable documents

19. 3. 2015

Parsing XML

by Martin Kruliš (v1.0) 10

XPath Query Language◦ Inspired by filesys. paths (elements ~ directories)◦ Various types of queries that yield

Boolean, number, string, or set of DOM nodes◦ Quite expressive (num. operations, conditions, …)

XSLT Transformations◦ XSLT describes transformation of one XML

document to another (or to HTML, or to plain-text) XSLT rules are stored in XML document

◦ Uses XPath for search queries◦ Turing complete language

19. 3. 2015

XPath and XSLT

by Martin Kruliš (v1.0) 11

XML Utilities in PHP◦ SAX parser◦ DOM API and parser◦ XPath query engine (over a DOM API)◦ XSLT processor◦ PHP-specific Simple XML API (simplified DOM)

Most of the API is object oriented◦ DOM is object oriented by design◦ Simple XML is based on specific properties of PHP

classes (e.g., iterators or magic methods)

19. 3. 2015

XML and PHP

by Martin Kruliš (v1.0) 12

Event Driven Parsing◦ The document is processed as a stream

In a single call of xml_parse()◦ Important encounters are reported via callbacks

xml_set_element_handler() xml_set_character_handler() …

19. 3. 2015

PHP SAX Parser

Example 1

by Martin Kruliš (v1.0) 13

Document Object Model in PHP◦ Set of PHP-native classes◦ Implementing DOM 3 as defined by W3C

DOMDocument – entire XML document DOMElement – tree node of one XML element DOMAttr – attribute of an element DOMNode – base class for all tree classes DOMCharacterData – plain text contents …

19. 3. 2015

PHP DOM Implementation

by Martin Kruliš (v1.0) 14

Document Validation◦ DOMDocument methods for validation

validate(), schemaValidate() Automatic validation when the document is parsed

If validateOnParse == true

DOMXPath Class for XPath Search◦ Operates on DOMDocument◦ Search is performed by query() or evaluate()◦ The result is either basic PHP type (boolean, float, or string) or DOMNodeList object

19. 3. 2015

PHP XML Validation and XPath

Example 2

by Martin Kruliš (v1.0) 15

XSLTProcessor Class◦ Uses libxslt external library◦ Transformation rules are loaded from a DOM

document or from a Simple XML Element◦ Transformation input is a DOMDocument object◦ The result is yielded

As a new DOMDocument object String with serialized XML/HTML/text document Directly to a file

19. 3. 2015

PHP and XSLT

Example 3

by Martin Kruliš (v1.0) 16

Simplified DOM API◦ Also loads the document into tree structure◦ All nodes are SimpleXMLElement objects

Tree traversal is implemented by overloading class iterators and magic methods __get(), __set(), …

◦ The structure can be modified and saved◦ Some advanced functions are also available

Integrated XPath query processor Conversions to/from DOM structure

19. 3. 2015

Simple XML in PHP

Example 4

by Martin Kruliš (v1.0) 17

JavaScript Object Notation (JSON)◦ Lightweight interchange format for structured

data◦ Based on subset of JavaScript language◦ Otherwise language independent

Many parsers exist with frontends for many languages

◦ Intended for replacing XML in simple scenarios

Syntax◦ Two basic structures: collections and lists◦ Supports strings, numbers, bools, and null type◦ Unicode safe

19. 3. 2015

JSON - Revision

by Martin Kruliš (v1.0) 18

JSON Example[ { "StudentId": 42, "Name": "John Smith" }, { "StudentId": 54, "Name": "Jane Johnson", "Graduated": true }]

19. 3. 2015

JSON – Revision

Ordered list

Named collection

Number (int)

Unicode string

Boolean literal

by Martin Kruliš (v1.0) 19

JSON Functions◦ json_decode() – JSON string -> object/array struct.◦ json_encode() – serialize any PHP type (except

resource) into JSON string◦ json_last_error(), json_last_error_msg()

Customizing Serialization Process◦ JsonSerializable interface◦ Abstract method jsonSerialize() that converts

object into anything that can be processed by json_encode()

19. 3. 2015

JSON in PHP

by Martin Kruliš (v1.0) 20

Image Processing in PHP

Martin Kruliš

19. 3. 2015

by Martin Kruliš (v1.0) 21

PHP: Hypertext Preprocessor◦ Not restricted only to (hyper)text◦ HTTP with MIME can accommodate any content

Compressed packages (zip, tar.gz, …) Application documents (PDF, …) Images

Caveats◦ PHP is text oriented

Binary data are represented as strings◦ PHP is interpreted

Processing binary data might be slow

19. 3. 2015

Non-textual Data

by Martin Kruliš (v1.0) 22

GD Library◦ The php_gd2 module◦ Supports various formats (JPEG, GIF, PNG, …)

Working with Images◦ Image is a resource$image = imagecreate(400, 300);

◦ Large variety of functions for manipulation◦ Image is not compressed in internal

representation◦ Can be saved or written to output

imagepng(), imagejpg(), imagegif() Corresponding MIME type needs to be set

19. 3. 2015

Images in PHP

by Martin Kruliš (v1.0) 23

Functions◦ Loading/saving supported formats◦ Basic pixel operations◦ Drawing simple geometric shapes

Lines, circles, polygons, …◦ Text rendering

Built-in fonts, PostScript fonts, TrueType fonts◦ Transformation and resampling◦ Copying, alpha blending

Functions are version specific◦ And time/memory demanding

19. 3. 2015

GD Library

Example 5

by Martin Kruliš (v1.0) 24

Exchangeable Image File Format◦ Metadata for photographs◦ Extension of JPEG and TIFF containers

PHP API◦ Read only functions◦ exif_imagetype() – returns image type◦ exif_read_data() – reads meta-data from image◦ exif_thumbnail() – returns the image thumbnail

(if present) as binary string

19. 3. 2015

EXIF

Example 6

by Martin Kruliš (v1.0) 25

Cairo◦ Fast 2D drawing library written in C◦ Supports transformations and Bezier curves

Gmagic◦ A Swiss army knife for image manipulation◦ Large variety of supported formats

ImageMagic◦ Well established library for image manipulation◦ Designed even for more complex operations

19. 3. 2015

Other Libraries

by Martin Kruliš (v1.0) 26

PHP and Database Management

SystemsMartin Kruliš

19. 3. 2015

by Martin Kruliš (v1.0) 27

MySQL Revision◦ Original mysql API is deprecated (as of PHP 5.5)◦ MySQL Improved (mysqli) API

Dual object/procedural interface Procedural interface is similar to original (deprecated)

API Advanced connectivity features

Persistent connections, compression, encryption Directly supports transactions

◦ MySQL Native Driver (mysqlnd) extension More direct access to MySQL server Additional features (e.g., asynchronous queries)

19. 3. 2015

MySQL

by Martin Kruliš (v1.0) 28

MySQLi API◦ mysqli class – the connection to the DBMS

Manage controls, settings, info, stats, … Issue queries and multi-queries Performs transaction control

◦ mysqli_stmt class – SQL statement representation SQL statement preparation and configuration Argument bindings

◦ mysqli_result class – SELECT result wrapper Various methods for accessing data in the result

19. 3. 2015

MySQL

by Martin Kruliš (v1.0) 29

Extensions◦ mysqlnd_qc

Transparent cache for MySQL queries◦ mysqlnd_memcache

Special extension that utilizes InnoDB Memcache Translates SQL statements to Memcache protocol

◦ mysqlnd_uh Allows user to insert hooks for low-level calls Can be used for monitoring or auditing

◦ mysqlnd_mux Transparent client-side connection multiplexing

19. 3. 2015

MySQL

by Martin Kruliš (v1.0) 30

PostrgreSQL◦ Quite powerful alternative for MySQL◦ Similar API to MySQL

pg_connect(), pg_query(), …

SQLite◦ SQL engine running directly on filesystem◦ Small project, where regular DBMS is not available

Commercial Giants◦ MSSQL, Oracle, dBase, IBM DB2, …

19. 3. 2015

Other Database Systems

by Martin Kruliš (v1.0) 31

Abstract Database Layers◦ Solving the problem of portability

If the application refrains from using specific SQL statements

PHP Data Objects (PDO)◦ Generic interface for various RDBMS◦ Extension php_pdo, individual DB systems are in

separate extensions (php_pdo_mysql, …)◦ Simple object oriented API

PDO and PDOStatement classes Minimalistic, no special functions

19. 3. 2015

PDO Interface

by Martin Kruliš (v1.0) 3219. 3. 2015

Discussion