Introduction to Server- Development

Transcription

1 Introduction to Server- Side Development with PHP Chapter 8 Textbook to be published by Pearson Ed 2015 in early Pearson 2014 Fundamentals of Web Development

2 What is Server-Side Development The basic hosting of your files is achieved through a web server. Server-side development is much more than web hosting: it involves the use of a programming technology like PHP or ASP.NET to create scripts that dynamically generate content Consider distinction between client side and server side

3 Comparing Client and Server Scripts

4 Server-Side Script Resources So many tools in your kit

5 Web Development Technologies

6 Market Share Of web development environments

7 Web Server s Responsibilities A web server has many responsibilities: handling HTTP connections responding to requests for static and dynamic resources managing permissions and access for certain resources encrypting and compressing data managing multiple domains and URLs managing database connections managing cookies and state uploading and managing files

8 LAMP stack WAMP, MAMP, You will be using the LAMP software stack Linux operating system Apache web server MySQL DBMS PHP scripting language

9 Apache and Linux LA Consider the Apache web server as the intermediary that interprets HTTP requests that arrive through a network port and decides how to handle the request, which often requires working in conjunction with PHP.

10 Apache Continued Apache runs as a daemon on the server. A daemon is an executing instance of a program (also called a process) that runs in the background, waiting for a specific event that will activate it. When a request arrives, Apache then uses modules to determine how to respond to the request. In Apache, a module is a compiled extension (usually written in the C programming language) to Apache that helps it handle requests. For this reason, these modules are also sometimes referred to as handlers.

11 Apache and PHP PHP Module in Apache

12 Apache Threads Multi-thread and multi-process Apache runs in two possible modes: multi-process (also called preforked) multi-threaded (also called worker) The default installation of Apache runs using the multiprocess mode.

13 Apache Threads Multi-thread and multi-process

14 PHP Internals PHP itself is written in C There are 3 main modules 1. PHP core. The Core module defines the main features of the PHP environment, including essential functions for variable handling, arrays, strings, classes, math, and other core features. 2. Extension layer. This module defines functions for interacting with services outside of PHP. This includes libraries for MySQL, FTP, SOAP web services, and XML processing, among others. 3. Zend Engine. This module handles the reading in of a requested PHP file, compiling it, and executing it.

15 Section 3 of 5 QUICK TOUR OF PHP

16 Quick Tour PHP, like JavaScript, is a dynamically typed language. it uses classes and functions in a way consistent with other object-oriented languages such as C++, C#, and Java The syntax for loops, conditionals, and assignment is identical to JavaScript Differs when you get to functions, classes, and in how you define variables

17 PHP Tags The most important fact about PHP is that the programming code can be embedded directly within an HTML file. A PHP file will usually have the extension.php programming code must be contained within an opening <?php tag and a matching closing?> tag any code outside the tags is echoed directly out to the client

18 PHP Tags

19 HTML and PHP Two approaches

20 HTML and PHP Two approaches

21 Variables Variables in PHP are dynamically typed. Variables are also loosely typed in that a variable can be assigned different data types over time To declare a variable you must preface the variable name with the dollar ($) symbol. $count = 42;

22 Data Types Data Type Boolean Integer Float String Array Object Description A logical true or false value Whole numbers Decimal numbers Letters A collection of data of any type (covered in the next chapter) Instances of classes

23 Constants A constant is somewhat similar to a variable, except a constant s value never changes... in other words it stays constant. Typically defined near the top of a PHP file via the define() function once it is defined, it can be referenced without using the $ symbol

24 Constants

25 Writing to Output Hello World To output something that will be seen by the browser, you can use the echo() function. echo ("hello"); //long form echo "hello"; //shortcut

26 String Concatenation Easy Strings can easily be appended together using the concatenate operator, which is the period (.) symbol. $username = World"; echo "Hello". $username; Will Output Hello World

27 String Concatenation Example $firstname = "Pablo"; $lastname = "Picasso"; /* Example one: These two lines are equivalent. Notice that you can reference PHP variables within a string literal defined with double quotes. The resulting output for both lines is: <em>pablo Picasso</em> */ echo "<em>". $firstname. " ". $lastname. "</em>"; echo "<em> $firstname $lastname </em>";

28 Section 4 of 5 PROGRAM CONTROL

29 If else The syntax for conditionals in PHP is almost identical to that of JavaScript

30 If else Alternate syntax

31 Switch case Nearly identical

32 While and Do..while Identical to other languages

33 For Identical to other languages

34 Alternate syntax for Control Structures PHP has an alternative syntax for most of its control structures. In this alternate syntax the colon (:) replaces the opening curly bracket, while the closing brace is replaced with endif;, endwhile;, endfor;, endforeach;, or endswitch;

35 Include Files Organize your code PHP does have one important facility that is generally unlike other non web programming languages, namely the ability to include or insert content from one file into another.

36 Include Files Organize your code PHP provides four different statements for including files, as shown below. include "somefile.php"; include_once "somefile.php"; require "somefile.php"; require_once "somefile.php"; With include, a warning is displayed and then execution continues. With require, an error is displayed and execution stops.

37 Section 5 of 5 FUNCTIONS

38 Functions You mean we don t write everything in main? Just as with any language, writing code in the main function (which in PHP is equivalent to coding in the markup between <?php and?> tags) is not a good habit to get into. A function in PHP contains a small bit of code that accomplishes one thing. In PHP there are two types of function: user-defined functions and built-in functions. 1. A user-defined function is one that you the programmer define. 2. A built-in function is one of the functions that come with the PHP environment

39 Functions syntax While the example function in Listing 8.13 returns a value, there is no requirement for this to be the case.

40 Functions No return no big deal.

41 Call a function Now that you have defined a function, you are able to use it whenever you want to. To call a function you must use its name with the () brackets. Since getnicetime() returns a string, you can assign that return value to a variable, or echo that return value directly, as shown below. $output = getnicetime(); echo getnicetime(); If the function doesn t return a value, you can just call the function: outputfootermenu();

42 Parameters Parameters are the mechanism by which values are passed into functions. To define a function with parameters, you must decide how many parameters you want to pass in, and in what order they will be passed Each parameter must be named

43 Parameters Thus to call our function, you can now do it in two ways: echo getnicetime(1); // this will print seconds echo getnicetime(0); // will not print seconds

44 Parameter Default Values Now if you were to call the function with no values, the $showseconds parameter would take on the default value, which we have set to 1, and return the string with seconds.

45 Pass Parameters by Value By default, arguments passed to functions are passed by value in PHP. This means that PHP passes a copy of the variable so if the parameter is modified within the function, it does not change the original.

46 Pass Parameters by Reference PHP also allows arguments to functions to be passed by reference, which will allow a function to change the contents of a passed variable. The mechanism in PHP to specify that a parameter is passed by reference is to add an ampersand (&) symbol next to the parameter name in the function declaration

47 Value vs Reference

48 Variable Scope in functions All variables defined within a function (such as parameter variables) have function scope, meaning that they are only accessible within the function. Any variables created outside of the function in the main script are unavailable within a function. $count= 56; // outputs 0 or generates run- function testscope() { echo $count; time } testscope(); echo $count; // outputs 56 //warning/error

49 Global variables Sometimes unavoidable Variables defined in the main script are said to have global scope. Unlike in other programming languages, a global variable is not, by default, available within functions. PHP does allow variables with global scope to be accessed within a function using the global keyword

50 Section 1 of 7 DATABASES AND WEB DEVELOPMENT

51 Databases and Web Development This chapter covers the core principles of relational Database Management Systems (DBMSs). All database management systems are capable of managing large amounts of data, maintaining data integrity, responding to many queries, creating indexes and triggers, and more. The term database can refer to both the software (i.e., to the DBMS) and to the data that is managed by the DBMS.

52 MySQL We will be using MySQL There are many other open source and proprietary relational DBMS, including: PostgreSQL Oracle Database IBM DB2 Microsoft SQL Server MySQL

53 The Role of Databases In Web Development Databases provide a way to implement one of the most important software design principles: one should separate that which varies from that which stays the same

54 Separate that which varies That is, use a DB to store the content of pages. The program (PHP) determines which data to display, often from information in the GET or POST query string, and then uses a database API to interact with the database Although the same separation could be achieved by storing content in files on the server, databases offer intuitive and optimized systems that do far more than a file based design that would require custom-built reading, parsing, and writing functions.

55 That Which Changes Can be stored in the DB

56 Database Design Tables A database in a Relational DBMS is composed of one or more tables. A table is a two-dimensional container for data that consists of records (rows); Each record has the same number of columns, which are called fields, which contain the actual data. Each table will have one special field called a primary key that is used to uniquely identify each record in a table.

57 Tables in a Database Illustrated example

58 Section 5 of 7 ACCESSING MYSQL IN PHP

59 Database Connection Algorithm No matter what API you use, the basic database connection algorithm is the same: 1. Connect to the database. 2. Handle connection errors. 3. Execute the SQL query. 4. Process the results. 5. Free resources and close connection.

60 Database Connection Algorithm An illustration through example

61 Database Connection Algorithm An illustration through example

62 Handling Connection Errors We need to handle potential connection errors in our code. Procedural mysqli techniques use conditional (if...else) statements on the returned object from the connection attempt. The PDO technique uses try-catch which relies on thrown exceptions when an error occurrs.

63 Handling Connection Errors Procedural Approach

64 Handling Connection Errors Object-Oriented PDO with try-catch In addition PDO has 3 different error modes, that allow you to control when errors are thrown.

65 Execute the Query Procedural and Object-Oriented Both return a result set, which is a type of cursor or pointer to the returned data

66 Queries that don t return data Procedural and Object-Oriented

67 Integrating User Data Say, using an HTML form posted to the PHP script

68 Integrating User Data Not everyone is nice. While this does work, it opens our site to one of the most common web security attacks, the SQL injection attack.

69 SQL Injection Illustration From Chapter 16

70 Defend against attack Distrust user input The SQL injection class of attack can be protected against by Sanitizing user input Using Prepared Statements

71 Sanitize User Input Quick and easy Each database system has functions to remove any special characters from a desired piece of text. In MySQL, user inputs can be sanitized in PHP using the mysqli_real_escape_string() method or, if using PDO, the quote() method

72 Prepared Statements Better in general A prepared statement is actually a way to improve performance for queries that need to be executed multiple times. When MySQL creates a prepared statement, it does something akin to a compiler in that it optimizes it so that it has superior performance for multiple requests. It also integrates sanitization into each user input automatically, thereby protecting us from SQL injection.

73 Prepared Statements mysqli

74 Prepared Statements PDO

75 Prepared Statements Comparison of two techniques

76 Process Query Results mysqli

77 Process Query Results Mysqli using prepared statements

78 Fetch into an object Instead of an array Consider the following (very simplified) class: class Book { } public $id; public $title; public $copyrightyear; public $description;

79 Fetch into an object Instead of an array The property names must match exactly (including the case) the field names in the table(s) in the query

80 Fetch into an object A more flexible example, where class names needn t match DB fields

81 Freeing Resources And closing the connection

82 Using Transactions mysqli

83 Using Transactions PDO

84 Section 6 of 7 CASE STUDY SCHEMAS

85 Art Database

86 Book CRM Database Customer Relationship Management

87 Travel Photo Sharing Database

88 Section 7 of 7 SAMPLE DATABASE TECHNIQUES

89 Display a list of Links One of the most common database tasks in PHP is to display a list of links (i.e., a series of <li> elements within a <ul>).

90 Display a list of Links At its simplest, the code would look something like the following: $sql = "SELECT * FROM Categories ORDER BY CategoryName ; $result = $pdo->query($sql); while ($row = $result->fetch()) { echo '<li> ; echo '<a href="list.php?category='. $row['id']. '"> ; echo $row['categoryname']; echo '</a> ; echo '</li> ; }

91 Display a list of Links More maintainable version

92 Search and Results Page Visual of search box, results page, and no results page

93 Search and Results Page In this example, we will assume that there is a text box with the name txtsearch in which the user enters a search string along with a Submit button. The data that we will filter is the Book table; we will display any book records that contain the user-entered text in the Title field.

94 Search and Results Page To redisplay the search term we will add code like: <input type="search name="txtsearch placeholder="enter search string value="<?php echo $_GET['txtSearch'];?>" /> To where we generate the form. Unfortunately

95 Search and Results Page Problem to be solved

96 Editing a Record

97 Editing a Record