1. Web Programming Basics of PHP 1

2. Objectives To learn how to store and access data in PHP variables To understand how to create and manipulate numeric and string variables To review how to create HTML input forms To learn how to pass data from HTML forms to PHP scripts

3. PHP Variables All variable names begin with $ No type declarations – dynamically typed – don’t need to declare a variable before using it – don’t need to specify what type of data it will take (system decides dynamically) An unsigned variable has the value NULL String literals are defined with either single quotes (') or double quotes (") – $sum = 100.30; – print 'the sum is $sum';  the sum is $sum – print "the sum is $sum" ;  the sum is 100.30 3

4. Assigning New Values to Variables You can assign new values to variables: $days = 3; $newdays = 100; $days = $newdays; At the end of these three lines, $days and $newdays both have values of 100. 4

5. Selecting Variable Names You can select just about any set of characters for a variable name in PHP, but they must: – Use a dollar sign ($) as the first character – Use a letter or an underscore character (_) as the second character – Cannot start with a numeric character Note:Try to select variable names that help describe their function. For example $counter is more descriptive than $c or $ctr. 5

6. Combining Variables and the print Statement That is, to print out the value of $x, write the following PHP statement: – print "$x"; The following code will output "Brian is 6 years old". $age=6; print "Brian is $age years old."; What will the following output?: print 'Brian is $age years old.'; 6

7. A Full Example (prog4.php)... 1. <?php 2. $first_num = 12; 3. $second_num = 356; 4. $temp = $first_num; 5. $first_num = $second_num; 6. $second_num = $temp; 7. print "first_num= $first_num second_num=$second_num"; 8. ?>

8. Using Arithmetic Operators For example <?php $apples = 12; $oranges = 14; $total_fruit = $apples + $oranges; print "The total number of fruit is $total_fruit"; ?> These PHP statements would output "The total number of fruit is 26." 8

9. Common PHP Numeric Operators 9

10. A Full Example (prog5.php) <?php $columns = 20; $rows = 12; $total_seats = $rows * $columns; $ticket_cost = 3.75; $total_revenue = $total_seats * $ticket_cost; $building_cost = 300; $profit = $total_revenue - $building_cost; print "Total Number of Seats is $total_seats "; print "Each Ticket Costs $ticket_cost "; print "Total Revenue (Seats * Cost) is $total_revenue "; print "Building Cost is $building_cost "; print "Total Profit (Revenue - Building Cost) is $profit"; ?>

11. WARNING: Using Variables with Undefined Values 11 If you accidentally use a variable that does not have a value assigned to it will have no value (called a null value). When a variable with a null value is used in an expression PHP, PHP may not generate an error and may complete the expression evaluation. For example, the following PHP script will output x= y=4. <?php $y = 3; $y=$y + $x + 1; // $x has a null value print "x=$x y=$y"; ?>

12. Writing Complex Expressions Operator precedence rules define the order in which the operators are evaluated. For example, $x = 5 + 2 * 6; The value of $x is either 42 or 17 depending on order of evaluation. Since multiplication evaluated before addition operations, this expression evaluates to 17. 12

13. PHP Precedence Rules PHP follows the precedence rules listed below. – First it evaluates operators within parentheses (brackets). – Next it evaluates multiplication and division operators. – Finally it evaluates addition and subtraction operators. 13

14. A Full Example (prog6.php) 1. <?php 2. $mark1 = 50; 3. $mark2 = 100; 4. $mark3 = 75; 5. $average = ($mark1 + $mark2 + $mark3) / 3; 6. print "The marks are $mark1 $mark2 and $mark3 "; 7. print "The average is $average"; 8. ?> 14

15. Example to try <? ?> 15 Write a php script to calculate the volume of a box (length times height times width) assign values to variables calculate the volume print out a statement with the variables plus the result (volume)

16. Working with PHP String Variables Character strings are used to hold data such as names, addresses and descriptions. There is no practical limit to the length of a string in PHP Consider the following example. – $name="Christopher"; – $preference="Milk Shake"; $name is assigned "Christopher" and the variable $preference is assigned "Milk Shake". 16

17. WARNING: Be Careful Not to Mix Variable Types Be careful not to mix string and numeric variable types. For example, you might expect the following program to generate an error message, but it does not. Instead, it will output " sum=1 ". <?php $x ="banana"; $sum = 1 + $x; print ("sum=$sum"); ?> 17

18. Using the Concatenate Operator The concatenate operator (.) combines two separate string variables into one. – $fullname = $firstname. $lastname; – $fullname will receive the string values of $firstname and $lastname connected together. – <?php $firstname = "John"; $lastname = "Smith"; $fullname = $firstname. " ". $lastname; print "Fullname=$fullname" ; ?> Output: Fullname=John Smith 18

19. An Easier Way to Concatenate Strings You can also use double quotation marks to create concatenation directly (add strings together) For example $Fullname2 = "$FirstName $LastName"; – This statement has the same effect as $Fullname2 = $FirstName. " ". $LastName; 19

20. The strlen() Function Most string functions require you to send them one or more arguments. Arguments are input values that functions use in the processing they do. Often functions return a value to the script based on the input arguments. For example 20

21. The strlen() Function Example <?php $comments = "Good Job"; $len = strlen($comments); print "Length=$len"; ?> Output: Length=8 21

22. The trim() Function This function removes any blank characters from the beginning and end of a string. For example, consider the following script: <?php $in_name = " Joe Jackson "; $name = trim($in_name); print "in_name=$in_name$in_name "; print "name=$name$name"; ?> Output: in_name=Joe JacksonJoe Jackson name=Joe JacksonJoe Jackson 22

23. The strtolower() and strtoupper() Functions These functions return the input string in all uppercase or all lowercase letters, respectively. For example: <?php $inquote = "Now Is The Time"; $lower = strtolower($inquote); $upper = strtoupper($inquote); print ("upper=$upper lower=$lower"); ?> Output: upper=NOW IS THE TIME lower=now is the time 23

24. The substr() Function 24 Substr has the following general format:

25. Substring example <?php $name = "Ian Young"; $firstname = substr($name, 0, 3); $secondname = substr($name, 4, 5); print "firstname is $firstname and secondname is $secondname"; ?> 25 I A N Y O U N G 0 1 2 3 4 5 6 7 8

26. The substr() Function 26 The substr() function enumerates character positions starting with 0 (not 1) For example, in the string "Homer", the "H" would be position 0, the "o" would be position 1, the "m" position 2, and so on. For example <?php $date = "25/12/2002"; $month = substr($date, 0, 2); $day = substr($date, 3, 2); print ("Day=$day Month=$month"); ?> OUTPUT: Day=25 Month=12

27. The substr() Function 27 As another example, consider the following use of the substr() function It does not include the third argument (and thus returns a substring from the starting position to the end of the search string). <?php $date = "09/03/2006"; $year = substr($date, 6); //start at position 7 print ("Year=$year"); ?> OUTPUT: Year=2006

28. Example To Try Write a php script to: – assign your full name (first & second name) to one variable – use substr($variable, start, end) and substr($variable, start) to remove your firstname & surname from the string – count the number of characters in your first name and surname using strlen($variable) – print your firstname and surname name with the number of characters in each respectively 28

29. Other useful string functions strcmp(string1, string2) - compares 2 variables & returns 0 if values are exactly equal >0 if string1 is greater than (alphabetically after) string2 <0 of string 1 is less than (alphabetically before) string2 strpos(string1, string2) - returns starting position if string2 occurs inside string1 strrev(string) - reverses a string ltrim(string), rtrim(string) - removes extra spaces from beginning(left hand side), end (right hand side) of string 29

30. HTML Forms and not part of PHP language but important way to send data to scripts Creating HTML Input Forms Text Box Radio Buttons Check Box Select Box Text Area Submit/Reset button

31. Getting input data To receive data use a special global variable called $_POST. $name=$_POST[ " name " ]; 31 Enclose in square bracket and then quotes Name of HTML form variable (note do not use $) Special PHP Global variable. Technically it is an associative array (covered in chptr 5.) PHP variable name that you want to receive the HTML form input.

32. Sendingform.html A Simple Form Click submit to start our initial PHP program. Email: URL in browser http://localhost/~labuser/sendingform.html

33. Sendingform.html 33

34. Receive1.php Code The HTML form uses the following: Email: Then Receive1.php can receive input as follows : Receiving Input Thank You: Got Your Input. <?php $email=$_POST["email"]; print " Your email address is $email "; ?> These must match

35. Other global variables As well as $_POST there is $_GET & $_REQUEST $_GET works similarly to $_POST except URL will be displayed information sent in the browser's address bar (less secure) & limited to 100 characters $_REQUEST contains $_GET & $_POST (generalised request) 35

36. HTML Form Input Elements Textbox Radio Buttons Checkbox Selectbox option1 option2 Text area 36

37. Summary Variables are used to store and access data in computer memory. You can associate a value with a variable, change that value, print it out, and perform many different operations on it. PHP supports both numeric and string variables. String variables use different methods for value manipulation (for example, concatenation) than numeric variables do. 37

38. Summary You can use HTML forms to pass data to PHP scripts. HTML form elements include text boxes, text areas, password boxes, check boxes, radio buttons, and selection lists. PHP scripts can receive form element input values by using a PHP variable name that matches the one specified in the form element’s name argument. 38