David Lash DePaul University SNL 262 Web Page Design Web Wizard’s Chapter 3 Instructor: David A. Lash Controlling the instruction flow.

David Lash

DePaul University SNL 262

Web Page Design

Web Wizard’s Chapter 3

Instructor: David A. Lash

Controlling the instruction flow

2David Lash

What We Learned Last Time

PHP is a technology that can help create dynamic pages. PHP instructions run before HTML page is returned to

browser PHP output is mixed in with HTML statements

PHP instructions are placed within these tags<?php … ?>

PHP requires a more precise syntax that HTMLLooks like

print ( “ <br> Hello There <br>”);PHP instructions can only be interpreted on Web

server

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More of What We Learned Last Time

We can temporarily save data in PHP variables We can store numbers or character strings

$x = $y + 2; $apple = $x + 5; $first = “George”; $last = “Bush”; $full = “$first W. $last”;

We can pass data from HTML forms to PHP scripts The <form action=myscript.php method=post>

tag specifies next file to start. We specify data to pass as follows within the HTML form:

<input type=text name=“firstname”> Receive as follows within PHP:

$name=$_POST[‘firstname’];

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Objectives

So far we’ve received data but cannot do much behind mail that data to us.

Will look at: conditional test statements – Can use to look

at: Was needed data supplied? Test data vales – Is data > 50? Is aver > 90?

Look at testing more than one thing at once: Create compound conditional test statements

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Using Conditional Test Statements

Conditional statements provide a way for scripts to test for certain data values and then to react differently depending on the value found.

Will examine the if statement, the elseif clause, the else clause.

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Using the if Statement

Use an if statement to specify a test condition and a set of statements to run when a test condition is true.

if ($average > 69) {

$Grade="Pass";

print "Grade=$Grade ";

}

print "Your average was $average";

if $average was equal to 70 then the above would output: Your average was 70

When $average is greater than 69 execute these statements.

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Note the strange syntax

if ($average > 69) {

$Grade="Pass";

print "Grade=$Grade ";

}

print "Your average was $average";

Expression to test

When true do everything between the { }

Note how the if statement doesn’t use semicolons. But everything else does. Instead use the { … } block.

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Test Expressions

Test expressions use test operators within their expressions. Test operators work much like the expression

operators. The if statement above uses the greater than

(>) operator to test whether $average is greater than 69.

Test operators evaluate to true or false

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PHP Test Operators

Test Operator

Effect Example Result

== Equal to if ($x == 6){ $x = $y + 1; $y = $x + 1; }

Run the second and third statements if the value of $x is equal to 6.

!= Not equal to if ($x != $y) { $x = 5 + 1; }

Run the second statement if the value of $x is not equal to the value of $y.

< Less than if ($x < 100) { $y = 5; }

Run the second statement if the value of $x is less than 100.

> Greater than if ($x > 51) { print "OK"; }

Run the second statement if the value of $x is greater than 51.

>= Greater than or equal to

if (16 >= $x) { print "x=$x"; }

Run the second statement if 16 is greater than or equal to the value of $x.

<= Less than or equal to

if ($x <= $y) { print "y=$y"; print "x=$x"; }

Run the second and third statements if the value of $x is less than or equal to the value of $y.

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A Full Example ...

Consider the following application: Receives two grades as input and

determines whether their average is above 89.

It uses an HTML form for input grades: Enter First Score <input type="text" size="4” maxlength="7" name="grade1"> Enter Second Score <input type="text" size="4” maxlength="7" name="grade2">

Sets $grade1

Sets $grade2

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Receiving Code

1. <html>2. <head><title>Decisions</title></head>3. <body>4. <?php5. $grade1= $POST[“grade1”];6. $grade2= $POST[“grade2”];5. $average = ($grade1 + $grade2) / 2;6. if ( $average > 89 ) {7. print "Average score: $average You got an A! <br>";8. }9. $max=$grade1;10. if ($grade1 < $grade2) {11. $max = $grade2;12. }13. print ("Your max score was $max");14. ?>15. </body></html>

Get grade1 and grade2from HTML form.

Calculate average

Output if $average is more than 89

Set when $grade2 is more than $grade1

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Another more useful example1. <html>2. <head>3. <title>Survey Form</title>4. </head>5. <body>6. <h1>Class Survey</h1>7. <FORM METHOD="POST" ACTION="planet.php">8. What is the smallest planet in our solar system?9. <br> <input type=radio name=pick value='a'> Mercury10.<br> <input type=radio name=pick value='b'> Venus11.<br> <input type=radio name=pick value='c'> Pluto12.<br> <input type=radio name=pick value='d'> Our Moon

13.<br><input type="submit" value="Submit">14. <input type="reset" value="Erase">15.</form>16.</BODY>17.</HTML>

The front-end HTML form

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The receiving php 1. <html>2. <head>3. <title>Survey Form</title>4. </head>5. <body>6. <body>7. <Font size=5 color=black> Your Averages Are:</font>8. <form action="guessdice2.php" method=post>9. <?php10. $pick = $_POST[pick];11. $total_right = 0;12. if ( $pick == 'c' ) {13. print "You got question 1 right";14. $total_right = $total_right + 1;15. } else {16. print "You got question 1 wrong";17. }18. print "<br>pick=$pick total_right=$total_right";19.?>20.<br>21.</form> </body> </html>

The receiving file with PHP

http://condor.depaul.edu/~dlash/extra/Webpage/examples/planet.html

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Comparing StringsPHP represents strings using the ASCII (“ask-ee”)

code values.(American Standard Code for Information Interchange). ASCII provides a standard, numerical way to represent

characters on a computer. Every letter, number, and symbol is translated into a

code number.“A” is ASCII code 65, “B” is 66, “C” is 67, and so on.Lowercase “a” is ASCII code 97, “b” is 98, “c” is 99, and sASCII “A” is less than ASCII “a,” “B” is less than “b,” and “c” is less than

“d”.ASCII characters have ASCII code values lower than letters. So ASCII

character “1” is less than “a” or “A”

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Comparing Strings

You can use == operator to check if one string is equal to another. For example,

$name1 = "George"; $name2 = "Martha";

if ($name1 == $name2) {

print ("$name1 is equal to $name2" );

} else {

print ("$name1 is not equal to $name2");

}

Would output: “George is not equal to Martha”.

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Comparing Strings

Also can use <, >, <=, and >= operators to compare string values using ASCII code values.

For Example$name1 = "George"; $name2 = "Martha";

if ($name1 < $name2) {

print ("$name1 is less than $name2");

} else {

print ("$name1 is not less than $name2");

}

It would output “George is less than Martha”.

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A Full Example ...

Consider the following application: Compares two input strings. It uses the HTML form element that sets the

variables $first and $second.

First Name: <input type="text" size="10"

maxlength="15" name="first">

Second Name: <input type="text" size="10"

maxlength="15" name="second">

Sets $first

Sets $second

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Receiving Code

1. <html>

2. <head><title>String Comparison Results</title></head>

3. <body>

4. <?php

5. $first = $_POST[“first”];

6. $second = $_POST[“second”];

7. print ("First=$first Second=$second<br>");

8. if ($first == $second) {

9. print ("$first and $second are equal");

10. }

11. if ($first < $second) {

12. print ("$first is less than $second");

13. }

14. if ($first > $second) {

15. print ("$first is greater than $second");

16. }

17. ?></body></html>

Output if $first is equal to $second

Set when $second is less than $first

Set when $first is more than $second

Get the values of $first and $second

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The Output ...

The previous code can be executed at

http://webwizard.awl.com/~phppgm/C3/comparenames.html

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Using the elseif Clause

Use an elseif clause with an if statement to specify an additional test condition

if (test expression) {

one or more PHP statements

} elseif (test expression)


}

The above script checks the elseif test expression when the test condition for the if statement is false.

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Using the elseif Clause

One or more elseif clauses can be used with an if statement. if ($hour < 9) {

print "Sorry, it is too early.";

} elseif ($hour < 12) {

print "Good morning. The hour is $hour. ";

print "How can we help you?";


print "Sorry, we are out to lunch. ";


print "Good afternoon. The hour is $hour. ";

print "How can we help you?";

} elseif ($hour <= 23) {

print "Sorry, we have gone home already.";

}

Check this testexpression when thefirst three conditionsare all false.

Check this testexpression when thefirst two conditionsare all false.

Check this testexpression when thefirst condition is false.

if $hour == 15, output “Good afternoon. The hour is 15. How can we help you?” if $hour == 24, then this code outputs nothing.

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Using the else Clause

Use an else clause with if and possibly one or more elseif clauses Specify set of statements to run when all the

previous test conditions are false. Has the following general format shown in the

if (test expression) {


} else {


}

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Using the else Clause

For example, if $count had a value of –75, then this code would output “Illegal value for count = –75”

if ( $count == 0 ) { print ("Time to reorder.");

$reorder=1;

} elseif ( $count == 1 ) {

$reorder=1;

print ("Warning: we need to start reordering.");

} elseif ( $count > 1 ) {

$reorder = 0;

print ("We are OK for now.");

} else {

print ("Illegal value for count = $count");

}

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A Full Example ...

Full example that extends the grade-averaging to determine a letter grade (A, B, C, D, or F) and to catch illegal input.

Use the following HTML form for input Sets $grade1

Sets $grade2

Enter First Score <input type="text" size="4” maxlength="7" name="grade1">Enter Second Score <input type="text” size="4” maxlength="7" name="grade2">

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Receiving Code

1. <html> <head><title>Grade Calculation</title></head>

2. <body>

3. <?php

4. $grade1 = $_POST[“grade1”]; $grade2 = $_POST[“grade2”];

5. $average = ($grade1 + $grade2) / 2;

6. if ($average > 89) {

7. print ("Average=$average You got an A");

8. } elseif ($average > 79) {

9. print ("Average=$average You got a B");


11. print ("Average=$average You got a C");


13. print ("Average=$average You got a D");

14. } elseif ($average >= 0) {

15. print ("Grade=$grade You got an F");

16. } else {

17. print ("Illegal average less than 0 average=$average");

18. }

19. $max=$grade1;

20. if ($grade1 < $grade2) {

21. $max = $grade2;

22. }

23. print ("<br>Your max score was $max");

24. ?> </body></html>

Compute average of $grade1 and $grade2

Check if $averageis an “A”, “B”,”C”, “D”or “F”

Get values of $grade1 and $grade2

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Would output the following...

The previous code can be executed at http://perl-pgm.com/C3/decision.php

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Logical Test Operators

PHP supports three logical test operators.

1. &&—the AND operator. Use in if statements and while loops. Example: if ($ctr < $max && $flag == 0) {

Do instructions in brackets when$ctr < $max AND $flag is 0.

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Or operator

2. ||—the OR operator. Used much like the AND operator in if statements andwhile loops. Example, if ($ctr != $max || $flag == 0) {

Carries out the statements within the if statement if either $ctr is not equal to $max or $flag is equal to 0.

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Not operator

3. !—the NOT operator. Used to test whether an expression is false (used in while loops and in if statements). Example, if (!$flag == 0) {

This statement is true when $flag is anything except 0.

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Example Front End Form

Example asks the user to guess a “secret” two-digit combination, uses logical test operators.

The Input HTML form uses the following to set pick1. A similar group sets a variable pick2.

<font size=4 > Pick a number from 1 to 9 <br>

<input type="radio" name="pick1" value="1">1









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A Full Script Example …

1. <html><head><title>Number Guess Results </title><head>

2. <body>

3. <?php

4. $pick1 =$_POST[“pick1”]; $pick2 =$_POST[“pick2”];

5. $combo1=5;

6. $combo2=6;

7. if (($pick1 == $combo1) && ($pick2 == $combo2)) {

8. print ("Congratulations you got both secret numbers

$combo1 $combo2!");

9. } elseif (($pick1 == $combo1) || ($pick2 == $combo2)){

10. print ("You got one number right.");

11. } else {

12. print ("Sorry, you are totally wrong!");

13. }

14. print ("You guessed $pick1 and $pick2.");

15. ?></body></html>

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The Output ...

The previous code can be executed at

http://perl-pgm.com/C3/drivelogical.html

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Sending Form<html><head> <title> A Simple Form </title> </head><body><form action="http://condor.depaul.edu/~dlash/website/verify_it.php" method="post">

Please enter your name:<input type=text name=fname><br>Can we contact you?<input type=radio name=contact value=Yes> Yes<input type=radio name=contact value=No> No

<br> <input type="submit" value="Click To Submit"> <input type="reset" value="Erase and Restart"> </form>

</body> </html>

http://condor.depaul.edu/~dlash/extra/Webpage/examples/contact.html

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Receiving Script<html> <head> <title> Receiving Script </title> <body><?php $contact= $_POST["contact"]; $fname= $_POST["fname"];

if (!$_POST[‘contact’]) { print "Please supply a contact information <br>"; print “contact=$contact postcontact= $_POST[‘contact’]”; } elseif ( !$_POST[‘fname’] ) { print "Please supply a contact name <br>";

print “name=$fname postname=$_POST[‘fname’] <br>”;

} print "<hr> Contact=$contact name=$fname";?></body> </html>

Question: Why cann’t you do this test? if (!$contact) { instead of if( $_POST[‘contact’]) {

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Another Example … Consider average example

<html><head> <title>Survey Form</title></head><body><h1>Class Survey</h1><FORM METHOD="POST" ACTION="newaverage.php"> <br>Pick A Number: <BR> <input type=text name=num1> <br>Pick A Number 2: <BR><input type=text name=num2> <br>Pick A Number 3: <BR><input type=text name=num3>

<br><input type="submit" value="Submit"> <input type="reset" value="Erase"></form></BODY></HTML>

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PHP Code1. <html> <head> <title> Guess the Dice </title>2. <body>3. <Font size=5 color=black> Your Averages Are:</font>4. <form action="guessdice2.php" method=post>5. <?php6. $num1 = $_POST[num1];7. $num2 = $_POST[num2];8. $num3 = $_POST[num3];

9. if ( !$_POST[‘num1’] || !$_POST[‘num2’] || !$_POST[‘num3’]) {10. print "error please fill in values for all three numbers";11. print "num1=$num1 num2=$num2 num3=$num3";12. exit;13. }14. $aver = ($num1 + $num2 + $num3 ) / 3;

15. print "<font size=4 color=blue>";16. print "num1 = $num1 ";17. print "num2 = $num2 ";18. print "num3 = $num3 ";19. print "</font> <br> <font size=4 color=red>";20. print "<br>aver = $aver";21. print "</font> ";22. ?>23. <br>24. </form> </body> </html>http://condor.depaul.edu/~dlash/extra/Webpage/examples/newaverage.html

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One More Thing

You can implement very basic password access using the following form element: <input type=password name=pass>

You can then use conditional statements to verify password.

This is loose security. It sends password in unencryted between client and server. It will stop simple access to page (but not others in

directory.) Most use more sophisticated methods.

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Consider the following input form ...

<html><head> <title> A Simple Form </title> </head><body><form action="http://condor.depaul.edu/~dlash/website/checkpass.php" method="post">

Please enter your name:<input type=text name=fname><br>Please enter password:<input type=password name=pass>

<br> <input type="submit" value="Click To Submit">

<input type="reset" value="Erase and Restart"> </form> </body> </html>

You can view this at http://condor.depaul.edu/~dlash/website/formpass.html

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Here is the receiving code ...

<<html> <head> <title> Receiving Script </title> <body><?php $passwd= $_POST["pass"]; $fname= $_POST["fname"];

if ($passwd == "password" ) { print "Thank you $fname welcome <br>"; print "Here is my site's content"; } else { print "Hit the road jack you entered password=$passwd<br>"; print "Contact someone to get the passwd"; }?></body> </html>

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Summary Looked at using conditional statements

if statement elsif statement else statement

conditional statements have different formatif ( $x < 100 ) {

$x = $y + 1;$z = $y + 2;

} Can do multiple tests at once:

if ( $x < 100 && $name = “george” ) { $x = $y + 1;$z = $y + 2;

} Can test if variable(s) set from form if ( !$_POST[‘var1’] || !$_POST[‘var1’] ) {

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Validating and checking PHP?

http://hapedit.free.fr A Free editor for html, php and other

things.1. Need to download the tool 2. Need to download php and install on

windows machinehttp://www.php.net

David Lash DePaul University SNL 262 Web Page Design Web Wizard’s Chapter 3 Instructor: David A. Lash Controlling the instruction flow.

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