Lecture 7 PHP Basics. Web Engineering CC 552

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1 Lecture 7 PHP Basics Web Engineering CC 552

2 Overview n Overview of PHP n Syntactic Characteristics n Primitives n Output n Control statements n Arrays n Functions n WampServer

3 Origins and uses of PHP n Origins - Rasmus Lerdorf Developed to allow him to track visitors to his Web site n PHP is an open-source product n PHP is an acronym for Personal Home Page, or PHP: Hypertext Preprocessor n PHP is used for form handling, file processing, and database access

4 PHP Overview n PHP is a server-side scripting language whose scripts are embedded in XHTML documents Similar to JavaScript, but on the server side n PHP is an alternative to CGI, ASP.NET and Java servlets n PHP syntax is similar to that of JavaScript n PHP is dynamically typed n PHP is purely interpreted

5 PHP Overview (2) n PHP is very popular for Web sites. PHP is installed on more than 20 million websites. n Facebook, Yahoo and Wikipedia are using PHP.

6 PHP: Server-Script Language PHP is the most widely-used, free The PHP syntax is very similar to Perl and C. PHP is often used together with Apache (web server) on various operating systems. It also can be used with Microsoft's IIS on Windows. PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.) PHP is an open source software (OSS)

7 PHP File (1) What is a PHP File? n PHP files may contain text, HTML tags and scripts n PHP files are returned to the browser as plain HTML n PHP files have a file extension of ".php", or ".phtml"

8 PHP File (2) n PHP code can be specified in an XHTML document internally or externally: n Internally: <?php...?> n Externally: include ("myscript.inc") the file can have both PHP and XHTML If the file has PHP, the PHP must be in <?php..?>, even if the include is already in <?php..?>

9 Example <html> <head> <title>php says hello</title> </head> <body> <?php print "Hello, World!";?> </body> <html> <head> <title>php says hello</title> </head> <body> hello, World! </body> </html> </html>

10 Interaction between client, Web server

11 Interaction between client, Web server

12 The popularity of PHP n n n It s fast: On Web sites, because it is embedded in HTML code, the time to process and load a Web page is short. It s free. It s easy to use: The syntax is simple and easy to understand and use, even for non-programmers. For use in Web sites, PHP code is designed to be included easily in an HTML file. n It s versatile: PHP runs on a wide variety of operating systems Windows, Linux, Mac OS, and most varieties of Unix. n n n Technical support is widely available: You can join one of several discussion lists offered on the PHP Web site ( It s secure: As long as your scripts are designed correctly, the user does not see the PHP code. It s customizable: The open source license allows programmers to modify the PHP software, adding or modifying features as needed to fit their own environments.

13 Files and System Commands Using PHP with your file system n PHP can interact with your file system the directories and files that are on your local hard disk or on other computers accessible over a network. PHP can write into a file on your file system, creating the file if it doesn t exist, and can read the contents from files. It can also create directories, copy files, rename files, delete files, change file attributes, and perform many other file system tasks. Using PHP for system commands n PHP can interact with your operating system to perform any task the operating system can perform. You can execute an operating system command and receive the output. For example, you can execute a dir command (to list the files in your directory) from PHP and receive the list of filenames that the dir/ls command produces.

14 PHP 5 n Most of the important changes in PHP version 5 don t affect the coding or the use of PHP. They affect the performance of PHP. The Zend engine (the magic, invisible engine that powers PHP) has been significantly improved, and as a result, scripts run faster and more efficiently. n The object-oriented programming features of PHP are a major focus of PHP 5. The creation and use of objects runs much faster, many object-oriented features have been added, and exceptions are introduced. n PHP 5 adds support for MySQL 4.1 and later.

15 Syntactic Characteristics n Every variable name begins with a $ Case sensitive n Comments - three different kinds (Java and Perl) //... #... /*... */ n PHP statements terminated with ; n Compound statements are formed with braces n Compound statements cannot define locally scoped variables (except functions)

16 Reserved words of PHP n These are not case sensitive!

17 Variables n There are no type declarations n An unassigned (unbound) variable has the value NULL n The unset function sets a variable to NULL n The IsSet function is used to determine whether a variable is set n error_reporting(15); the interpreter will report when an unbound variable is referenced

18 Variables (cont.) n empty($varname) : True if value is 0 or is a string with no characters in it or is not set. n Other functions: is_int($number), is_array($var2), is_float($number), is_null($var1), is_numeric($string), is_string($string)

19 Primitives n Four scalar types: Boolean, integer, double, and string n Two compound types: array and object n NULL is a special type n Integer & double are like those of other languages n Boolean - values are true and false (case insensitive)

20 Strings n Characters are single bytes n String literals use single or double quotes n Single-quoted string literals (Unparsed Strings) Embedded variables are NOT expanded and embedded escape sequences are NOT recognized n Double-quoted string literals (Parsed Strings) Embedded variables ARE expanded and embedded escape sequences ARE recognized e.g., $var = "Bob"; $Var = "Joe"; echo "$var, \t $Var"; // outputs "Bob, Joe"

21 Concatenation Operator n This operator is represented by a period (.) character n used to combine two separate variables (usually strings) into a single string <?php $string = "Thank you for buying "; $newstring = $string. "my book!";?>

22 Simple Mathematics with PHP Variables PHP does multiplication and division first, and then addition and subtraction. The arithmetic inside the parentheses is performed first Operator + - * Description Addition Subtraction Multiplication Example x=2 x+2 x=2 5-x x=4 x*5 Result <?php $answer = 5 + 4; /* $answer now equals 9 */ $answer = $answer - 5; /* $answer now equals 4 */ / % Division division remainder Increment Decrement 15/5 5/2 5%2 10%8 10%2 x=5 x++ x=5 x x=6 x=4 $answer = $answer / 2; /* $answer now equals 2 */ $answer = 1/3; /* $answer is now */ $answer = ((5 + 4)*2) % 7; /* $answer now equals 4 */?>

23 Shorthand Mathematics in PHP Operator Example Is The Same As = += -= *= x=y x+=y x-=y x*=y x=y x=x+y x=x-y x=x*y $x=5; $y=7; $x.=$y; 57 /= x/=y x=x/y.= x.=y x=x.y %= x%=y x=x%y <?php $answer = 5; /* Assign Original value */ $answer += 2; /* Equivalent to: $answer = $answer + 2; */ $answer *= 2; /* Answer is now 14 */ $answer %= 5; /* Answer is now 4 */ <

24 Comparison Operators $first == $second $first === $second $first!= $second $first!== $second $first < $second $first > $second $first <= $second $first >= $second True if $first equals $second True if $first equals $second, and $first and $second are of the same type True if $first doesn't equal $second True if $first doesn't equal $second or $first and $second are different types True if $first is less than $second True if $first is more than $second True if $first is less than or equal to $second True if $first is more than or equal to $second

25 Predefined functions n Arithmetic functions floor, ceil, round, abs, min, max, rand, etc. n String functions strlen, strcmp, strpos, substr chop remove whitespace from the right end trim remove whitespace from both ends ltrim remove whitespace from the left end strtolower, strtoupper

26 Scalar type conversions n Implicit type conversion coercion String to numeric $foo = 1 + "10 Small Pigs"; // $foo is integer (11) If the string contains an e or an E, it is converted to double; otherwise to integer $foo = 1 + "-1.3e3"; // $foo is double (-1299) If the string does not begin with a sign or a digit, zero is used $foo = 1 + "bob3"; // $foo is integer (1) n Explicit conversions casts e.g., (int)$total or intval($total) or settype($total, "integer") n The type of a variable can be determined with gettype or is_type function e.g.: gettype($total) may return "unknown" is_integer($total) returns Boolean value

27 Output n Output from a PHP script is XHTML that is sent to the browser n There are three ways to produce output: echo, print, and printf echo and print take a string, but will coerce other values to strings echo Hello there!"; echo( Hello there! ); echo $sum; print "Welcome!"; print( Wellcome ); n today.php (too see actual PHP script) n

28 Control statements n Selection if, else, else if switch n Loops The switch expression type must be integer, double, or string while, do-while, for powers.php

29 Arrays n Not like the arrays of any other programming language A PHP array is a generalization of the arrays of other languages n A PHP array is really a mapping of keys to values, where the keys can be numbers (to get a traditional array) or strings (to get a hash)

30 Array creation n Use the array() construct, which takes one or more key => value pairs as parameters and returns an array of them The keys are non-negative integer literals or string literals The values can be anything $list1 = array(); $list2 = array (17, 24, 45, 90); $list3 = array(0 => "apples", 1 => "oranges", 2 => "grapes") $list4 = array( Joe => 42, Mary => 41, Jan => 17);

31 Accessing array elements n Individual array elements can be accessed through subscripting $list[4] = 7; $list["day"] = "Tuesday"; n The keys or values can be extracted from an array $highs = array("mon" => 74, "Tue" => 70, "Wed" => 67, "Thu" => 62, "Fri" => 65); $days = array_keys($highs); $temps = array_values($highs);

32 Dealing with arrays n An array can be deleted with unset unset($list); unset($list[4]); // No index 4 element now n is_array($list) returns true if $list is an array n in_array(17, $list) returns true if 17 is an element of $list n explode(" ", $str) creates an array with the values of the words from $str, split on a space n implode(" ", $list) creates a string of the elements from $list, separated by a space

33 Sequential access to array elements n next and prev functions $citites = array( London, Paris, Chicago ); $city = next($cities) //$city = Paris n foreach statement to build loops that process all of the elements in an array foreach (array as scalar_variable) loop body E.g. foreach ($list as $temp) print ( $temp ); foreach (array as key=>value) loop body E.g. foreach ($lows as $day=>$temp) print( The low temperature on $day was $temp );

34 Sorting arrays n sort - to sort the values of an array, leaving the keys in their present order - intended for traditional arrays e.g., sort($list); Works for both strings and numbers, even mixed strings and numbers $list = ('h', 100, 'c', 20, 'a'); sort($list); // Produces ('a', 'c', 'h, 20, 100) n asort - to sort the values of an array, but keeping the key/value relationships. n ksort to sort given array by keys rather than values sorting.php

35 Functions function function_name([formal_parameters]) { } n Functions need not be defined before they are called n Function overloading is not supported If you try to redefine a function, it is an error n Function names are NOT case sensitive n The return statement is used to return a value If there is no return, there is no returned value

36 Function parameters n If the caller sends too many actual parameters, the function ignores the extra ones n If the caller does not send enough parameters, the unmatched formal parameters are unbound n The default parameter passing method is pass by value (one-way communication) n To specify pass-by-reference, pre-append an ampersand to the formal parameter function addone(&$param) { $param++; } $it = 16; addone($it); // $it is now 17

37 Scope and Lifetime of Variables n Variables defined in a function have local scope n To access a non-local variable in a function, it must be declared to be global (within the function code) $b = 2; Function Sum () { global $b; $b = $b + 5; } Sum (); echo $b; // prints 7

38 Scope and Lifetime of Variables (2) n Normally, the lifetime of a variable in a function is from its first appearance to the end of the function s execution n To support history sensitivity a function must have static local variables static $sum = 0; Its lifetime ends when the browser leaves the document in which the PHP script is embedded fun.php

39 WAMP: Apache, MySQL, PHP on Windows n WampServer is a Windows web development environment. n It allows you to create web applications with Apache, PHP and the MySQL database. n It comes with PHPMyAdmin and SQLiteManager to easily manage databases. n WampServer 2.2 Includes : - Apache MySQL PHP

40 Summary n Overview of PHP n Syntactic Characteristics n Primitives n Output n Control statements n Arrays n Functions n WampServer

- Origins - Rasmus Lerdorf Developed to allow him to track visitors to his Web site

- Origins - Rasmus Lerdorf Developed to allow him to track visitors to his Web site 9.1 Origins and Uses of PHP - Origins - Rasmus Lerdorf - 1994 - Developed to allow him to track visitors to his Web site - PHP was originally an acronym for Personal Home Page, but later it became PHP: