CHAPTER 3

MORE ON FORM HANDLING

INCLUDING MULTIPLE FILES

WRITING FUNCTIONS

FORM VALIDATION

Useful functions:Name Description Best use

empty($var) Returns TRUE if the variable has been set and is not NULL

Text input

isset($var) Returns TRUE if the variable hasn't been set, contains a NULL value, or contains an empty string.

Non-text input: radio buttons, check boxes, submit. etc.

is_numeric ($var) Returns TRUE if the variable is a number or a string that can be converted to a number

FORM HANDLING REVISITED

Recall from Chapter 2 form handling with two pages:

One page displays the form

The second page processes it

Instead, both parts can be written into one page with a conditional:

if the form has been submitted

process the data

else

display the form

BOOK EXAMPLE REVISED<?php

// Check for form submission:

if (isset($_POST['submit'])) {

//calculate and print results

} ?>

<h1>Trip Cost Calculator</h1>

<form method="post"> <!-- no action attribute causes form to submit back to same page --> <!-- Display form inputs -->

<input type="submit" name="submit" value="Calculate!">

</form>

Complete code: http://people.uncw.edu/mferner/CSC475/DataFiles/Ch03/calculator.php

REVISED BOOK EXAMPLE WITH FORM VALIDATION// Check for form submission:

if (isset($_POST['submit'])) {

// Minimal form validation:

if (isset($_POST['distance'], $_POST['gallon_price'], $_POST['efficiency']) && is_numeric($_POST['distance']) && is_numeric($_POST['gallon_price']) && is_numeric($_POST['efficiency']) ) {

//calculate and print results

}

else { //invalid inputecho '<h1>Error!</h1><p>Please enter a valid distance, price per gallon, and fuel efficiency.</p>';}

}

Complete code: http://people.uncw.edu/mferner/CSC475/DataFiles/Ch03/calculator_validate.php

STICKY FORMS

The form remembers your previous entries.

• Text input: use the value attribute to print the variable if it exists.

• Radio buttons or check-boxes: add the code checked="checked" to the input tags if that value was selected.

• Textarea input: since there is no value attribute, just print the variable (if it is empty, nothing will show.)

• To preset a selection list, use the selected attribute.

Complete code:http://people.uncw.edu/mferner/CSC475/DataFiles/Ch03/calculator_sticky.php

INCORPORATING EXTERNAL FILES

include() and require() are equivalent when there are no problems – they differ in how they handle errors:

• include() – if include() fails, a warning will display, but the script will continue to run

• require() – if require() fails, and error is displayed, and the script is halted

Relative or absolute referencing may be used – relative is preferable

include_once() and require_once() are available for more complex code but cause extra work and thus potential slow-downs

ABSOLUTE VS RELATIVE PATHS• An absolute path references a file starting from the root

directory of the server:

include('C:/php/includes/file.php');

include('/usr/home/public_html/php/includes/file.php');

• A relative path uses the referencing (parent) file as the starting point.

• It will remain accurate even if the site is moved to another server.

• To move up one folder, use two periods

• To move into a folder, use its name followed by /

include('../ex2/file.php');

SEPARATING PAGE PARTS

header.html

footer.html

index.php

A SIMPLE FILE STRUCTURE

index.phpincludes(folder)

header.html

footer.html

style.css

images(folder)

MORE COMPLEX FILE STRUCTURES

Use MVC pattern:

• Model: contains files that manage the data or that interface with the database

• View: contains the files that represent the user interface

• Controller: contains files that receive the HTTP requests from browsers

www.sitepoint.com

USER-DEFINED FUNCTIONS• Function names are case insensitive (unlike variable

names)

• Syntax:

function function_name() {

// function code

}

• Uses

• associate repeated code with one function call• separate out sensitive or complicated processes from

other code• make common code bits easier to reuse

FUNCTIONS AND ARGUMENTS EXAMPLEUse a function to create the radio buttons in the car calculator program:

// This function creates a radio button.

// The function takes one argument: the value.

// The function also makes the button "sticky".

function create_gallon_radio($value) {

// Start the element:

echo '<input type="radio" name="gallon_price" value="' . $value . '"';

// Check for stickiness:

if (isset($_POST['gallon_price']) && ($_POST['gallon_price'] == $value)) {

echo ' checked="checked"';

}

echo " /> $value "; // Complete the element

} // End of create_gallon_radio() function.

CALLING THE FUNCTION<form action="calculator.php" method="post">

<p>Distance (in miles): <input type="text" name="distance" value="<?php if (isset($_POST['distance'])) echo $_POST['distance']; ?>" /></p>

<p>Ave. Price Per Gallon:

<?php

create_gallon_radio('3.00');

create_gallon_radio('3.50');

create_gallon_radio('4.00');

?>

</p>

…

RETURNING VALUES FROM FUNCTIONSPHP functions may or may not return values

print will return a 1 (success) or a 0 (fail)

echo does not return anything

Use return()

Example:

function calculate_trip_cost($miles, $mpg, $ppg) {

// Get the number of gallons:

$gallons = $miles/$mpg;

// Get the cost of those gallons:

$dollars = $gallons/$ppg;

// Return the formatted cost:

return number_format($dollars, 2);

} // End of calculate_trip_cost() function.