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Fortune Smiles - PHP

Now that you've got the basics of PHP variables and operators down, the second article in this series takes a look at PHP's form-processing capabilities, and introduces you to the comparison and logical operators and the "if-else" and "switch" family of conditional statements.

TABLE OF CONTENTS:
  1. PHP 101 (Part 2) - Shakespeare's Rose
  2. Form...
  3. ...And Function
  4. Operating With Extreme Caution
  5. Shakespeare In The Matrix
  6. If Not This, Then What?
  7. Fortune Smiles
  8. Submitting To The King
  9. Miscellaneous Notes
By: Vikram Vaswani and Harish Kamath, (c) Melonfire
Rating: starstarstarstarstar / 11
August 08, 2000

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PHP also provides you with a way of handling multiple possibilities - the "if-elseif-else" construct. A typical "if-elseif-else" statement block would look like this:

if (first condition is true) { do this! } elseif (second condition is true) { do this! } elseif (third condition is true) { do this! } ... and so on ... else { do this! }
And here's an example that demonstrates how to use it:


<html> <head> <style type="text/css"> td {font-family: Arial;} </style> </head> <body> <font face="Arial" size="+2"> The Amazing Fortune Cookie Generator </font> <form method="GET" action="cookie.php4"> <table cellspacing="5" cellpadding="5" border="0"> <tr> <td align="center"> Pick a day </td> <td align="right"> <select name="day"> <option value="Monday">Monday <option value="Tuesday">Tuesday <option value="Wednesday">Wednesday <option value="Thursday">Thursday <option value="Friday">Friday <option value="Saturday">Saturday <option value="Sunday">Sunday </select> </td> </tr> <tr> <tr> <td colspan="2" align="center"> <input type="submit" value="Hit me!"> </td> </tr> </table> </form> </body> </html>
As you can see, this is simply a form which allows you to pick a day of the week. The real work is done by the PHP script "cookie.php4"


<? if ($day == "Monday") { $fortune = "Never make anything simple and efficient when a way can be found to make it complex and wonderful."; } elseif ($day == "Tuesday") { $fortune = "Life is a game of bridge -- and you've just been finessed."; } elseif ($day == "Wednesday") { $fortune = "What sane person could live in this world and not be crazy?"; } elseif ($day == "Thursday") { $fortune = "Don't get mad, get interest."; } elseif ($day == "Friday") { $fortune = "Just go with the flow control, roll with the crunches, and, when you get a prompt, type like hell."; } else { $fortune = "Sorry, closed on the weekend"; } ?> <html> <head> <basefont face="Arial"> </head> <body> Here is your fortune for <? echo $day; ?>: <br> <b><? echo $fortune; ?></b> </body> </html>
In this case, we've used the "if-elseif-else" control structure to assign a different fortune to each day.

There's one important point to be noted here - as soon as one of the "if" statements within the block is found to be true, PHP will execute the corresponding code, skip the remaining "if" statements in the block, and jump immediately to the lines following the entire "if-elseif-else" block.{mospagebreak title=A Little Bit Of Logic} Now, you've already seen that PHP allows you to nest conditional statements. However, if you take another look at the example we used to demonstrate the concept


<? if ($day == "Thursday") { if ($time == "12") { if ($place == "Italy") { $lunch = "pasta"; } } } ?>
you'll agree that is both complex and frightening. And so, in addition to the comparison operators we've used so liberally thus far, PHP also provides a few logical operators which allow you to group conditional expressions together. The following table should make this clearer.

Operator

What It Means

Example

Evaluates To

&&

AND

$delta == $gamma && $delta > $omega

True

$delta && $omega < $omega

False

||

OR

$delta == $gamma || $delta < $omega

True

$delta > $gamma || $delta < $omega

False

!

NOT

!$delta

False

<=

is less than or equal to

$delta <= $omega

False



Given this knowledge, it's a simple matter to rewrite the example above in terms of logical operators:

<? if ($day == "Thursday" && $time == "12" && $place == "Italy") { $lunch = "pasta"; }
Simple and elegant? Yes.{mospagebreak title=Switching Things Around} An alternative to the "if-else" family of control structures is PHP's "switch" statement, which does almost the same thing. It looks like this


switch (decision-variable) { case first_condition_is true: do this! case second_condition_is true: do this! case third_condition_is true: do this! ... and so on... }
We'll make this a little clearer by re-writing our fortune cookie example in terms of the "switch" statement.

[cookie.php4]

<? // the decision variable here is the day chosen by the user switch ($day) { // first case case "Monday": $fortune = "Never make anything simple and efficient when a way can be found to make it complex and wonderful."; break; // second case case "Tuesday": $fortune = "Life is a game of bridge -- and you've just been finessed."; break; case "Wednesday": $fortune = "What sane person could live in this world and not be crazy?"; break; case "Thursday": $fortune = "Don't get mad, get interest."; break; case "Friday": $fortune = "Just go with the flow control, roll with the crunches, and, when you get a prompt, type like hell."; break; // if none of them match... default: $fortune = "Sorry, closed on the weekend"; break; } ?> <html> <head> <basefont face="Arial"> </head> <body> Here is your fortune for <? echo $day; ?>: <br> <b><? echo $fortune; ?></b> </body> </html>
There are a couple of important keywords here: the "break" keyword is used to break out of the "switch" statement block and move immediately to the lines following it, while the "default" keyword is used to execute a default set of statements when the variable passed to "switch" does not satisfy any of the conditions listed within the block.

 
 
>>> More PHP Articles          >>> More By Vikram Vaswani and Harish Kamath, (c) Melonfire
 

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