03-forms.ppt.pptx

PHP Workshop ‹#›
Forms
(Getting data from users)

Forms: how they work
• We need to know..
1. How forms work.
2. How to write forms in XHTML.
3. How to access the data in PHP.

How forms work
Web Server
User
User requests a particular URL
XHTML Page supplied with Form
User fills in form and submits.
Another URL is requested and the
Form data is sent to this page either in
URL or as a separate piece of data.
XHTML Response

XHTML Form
• The form is enclosed in form tags..
<form
action=“path/to/submit/page”
method=“get”>
<!–- form contents -->
</form>

Form tags
• action=“…” is the page that the form
should submit its data to.
• method=“…” is the method by which the
form data is submitted. The option are
either get or post. If the method is get
the data is passed in the url string, if the
method is post it is passed as a separate
file.

Form fields: text input
• Use a text input within form tags for a
single line freeform text input.
<label for=“fn">First Name</label>
<input type="text"
name="firstname"
id=“fn"
size="20"/>

Form tags
• name=“…” is the name of the field. You
will use this name in PHP to access the
data.
• id=“…” is label reference string – this
should be the same as that referenced in
the <label> tag.
• size=“…” is the length of the displayed
text box (number of characters).

Form fields: password input
• Use a starred text input for passwords.
<label for=“pw">Password</label>
<input type=“password"
name=“passwd"
id=“pw"
size="20"/>

Form fields: text input
• If you need more than 1 line to enter data,
use a textarea.
<label for="desc">Description</label>
<textarea name=“description”
id=“desc“
rows=“10” cols=“30”>
Default text goes here…
</textarea>

Form fields: text area
• name=“…” is the name of the field. You
will use this name in PHP to access the
data.
• id=“…” is label reference string – this
should be the same as that referenced in
the <label> tag.
• rows=“…” cols=“..” is the size of the
displayed text box.

Form fields: drop down
<label for="tn">Where do you live?</label>
<select name="town" id="tn">
<option value="swindon">Swindon</option>
<option value="london”
selected="selected">London</option>
<option value=“bristol">Bristol</option>
</select>

Form fields: drop down
• name=“…” is the name of the field.
• id=“…” is label reference string.
• <option value=“…” is the actual data
sent back to PHP if the option is selected.
• <option>…</option> is the value
displayed to the user.
• selected=“selected” this option is
selected by default.

Form fields: radio buttons
<input type="radio"
name="age"
id="u30“
checked=“checked”
value="Under30" />
<label for="u30">Under 30</label>
<br />
<input type="radio"
name="age"
id="thirty40"
value="30to40" />
<label for="thirty40">30 to 40</label>

Form fields: radio buttons
• name=“…” is the name of the field. All
radio boxes with the same name are
grouped with only one selectable at a time.
• value=“…” is the actual data sent back
to PHP if the option is selected.
• checked=“checked” this option is
selected by default.

Form fields: check boxes
What colours do you like?<br />
<input type="checkbox"
name="colour[]"
id="r"
checked="checked"
value="red" />
<label for="r">Red</label>
<br />
<input type="checkbox"
name="colour[]"
id="b"
value="blue" />
<label for="b">Blue</label>

Form fields: check boxes
• name=“…” is the name of the field. Multiple
checkboxes can be selected, so if the button are
given the same name, they will overwrite
previous values. The exception is if the name is
given with square brackets – an array is returned
to PHP.
• value=“…” is the actual data sent back to PHP
if the option is selected.
• checked=“checked” this option is selected
by default.

Hidden Fields
<input type="hidden"
name="hidden_value"
value="My Hidden Value" />
• name=“…” is the name of the field.
• value=“…” is the actual data sent back
to PHP.

Submit button..
• A submit button for the form can be
created with the code:
<input type="submit"
name="submit"
value="Submit" />

Fieldset
• In XHTML 1.0, all inputs must be grouped within the form into
fieldsets. These represent logical divisions through larger forms. For
short forms, all inputs are contained in a single fieldset.
<form>
<fieldset>
<input … />
<input … />
</fieldset>
<fieldset>
<input … />
<input … />
</fieldset>
</form>

In PHP…
• The form variables are available to PHP in
the page to which they have been
submitted.
• The variables are available in two
superglobal arrays created by PHP called
$_POST and $_GET.

Access data
• Access submitted data in the relevant array for
the submission type, using the input name as a
key.
<form action=“path/to/submit/page”
method=“get”>
<input type=“text” name=“email”>
</form>
$email = $_GET[‘email’];

A warning..
NEVER TRUST USER INPUT
• Always check what has been input.
• Validation can be undertaken using
Regular expressions or in-built PHP
functions.

A useful tip..
• I find that storing the validated data in a
different array to the original useful.
• I often name this array ‘clean’ or
something similarly intuitive.
• I then *only* work with the data in $clean,
and never refer to $_POST/$_GET again.

Example
$clean = array();
if (ctype_alnum($_POST['username']))
{
$clean['username'] = $_POST['username'];
}

Filter example
$clean = array();
{
}
$clean = array();
Initialise an array to store
filtered data.

Filter example
$clean = array();
{
}
Inspect username to make
sure that it is alphanumeric.

Filter example
$clean = array();
{
}
If it is, store it in the array.

Is it submitted?
• We also need to check before accessing
data to see if the data is submitted, use
isset() function.
if (isset($_POST[‘username’])) {
// perform validation
}

PHP: Moving On..

Expressions and Operators

Reminder
• PHP is embedded within xhtml pages
within the tags: <?php … ?>
• The short version of these tags can also
be used: <? … ?>
• Each line of PHP is terminated, like
MySQL, with a semi-colon.

Reminder
• Variables are automatically initialised when
you start to use them.
e.g.
<?php
$name = ‘Rob’;
echo $name;
?>

Expressions
• Using variables within expressions to do
something is what PHP is all about.
<?php
$name = ‘Rob’;
echo $name;
?>
Expression
Operator

Some Types of Operator
• Arithmetic
• Assignment
• Bitwise
• Comparison
• Ternary
• Incrementing
/decrementing
• Logical
• String

String Operators
• Use a dot to concatenate two strings:
e.g.
$firstname = ‘Rob’;
$surname = ‘Tuley’;
// displays ‘Rob Tuley’
echo $firstname.’ ‘.$surname;

Arithmetic Operators
Example Name Result
$a + $b Addition Sum of $a and $b.
$a - $b Subtraction Difference of $a and $b.
$a * $b Multiplication Product of $a and $b.
$a / $b Division Quotient of $a and $b.
$a % $b Modulus Remainder of $a divided by $b.

Assignment Operators
Example Result
$a = $b Sets $b to the same value as $a.
$a += $b Equivalent to $a = $a + $b.
$a .= $b Equivalent to $a = $a.$b.

Combining Operators
• Note that you can combine operators, for
example use =, + and / in one expression:
$a = 4;
$b = 2;
$c = $a + $b + ($a/$b);
// $c has value 4+2+(4/2) = 8
• Brackets help group operators.

Comparison Operators
Example Name Result
$a == $b Equal TRUE if $a is equal to $b.
$a != $b Not equal TRUE if $a is not equal to $b.
$a <> $b Not equal TRUE if $a is not equal to $b.
$a < $b Less than TRUE if $a is strictly less than $b.
$a > $b Greater than TRUE if $a is strictly greater than $b.
$a <= $b Less than or equal to TRUE if $a is less than or equal to $b.
$a >= $b Gtr than or equal to TRUE if $a is greater than or equal to $b.

Comparisons
• Comparison expressions return a value of
TRUE (or ‘1’) or FALSE (or ‘0’).
e.g.
$a = 10;
$b = 13;
// result is true (‘1’)
echo $a < $b;

Incrementing/Decrementing
Example Name Effect
++$a Pre-increment Increments $a by one, then returns $a.
$a++ Post-increment Returns $a, then increments $a by one.
--$a Pre-decrement Decrements $a by one, then returns $a.
$a-- Post-decrement Returns $a, then decrements $a by one.

Logical Operators
Example Name Result
$a and $b And TRUE if both $a and $b are TRUE.
$a or $b Or TRUE if either $a or $b is TRUE.
$a xor $b Xor TRUE if either $a or $b is TRUE, but not both.
!$a Not TRUE if $a is not TRUE.
$a && $b And TRUE if both $a and $b are TRUE.
$a || $b Or TRUE if either $a or $b is TRUE.

Finally, a tricky one!
• A single ? is the ternary operator.
(expr) ? if_expr_true : if_expr_false;
• A test expression evaluates to TRUE or
FALSE.
•TRUE gives first result (before colon)
•FALSE gives second result (after colon)

Ternary Operator example
<?php
$a = 10;
$b = 13;
echo $a<$b ? ‘a smaller’:‘b smaller’;
// string ‘a smaller’ is echoed
// to the browser..
?>

Groups of variables
• So far, we have stored ONE piece of data
in each variable.
• It is also possible to store multiple pieces
of data in ONE variable by using an array.
• Each piece of data in an array has a key..

An array
Normal Variable, no key:
$name = ‘Rob’;
Array Variable, multiple pieces with ‘keys’:
$name[0] = ‘Rob’;
$name[1] = ‘Si’;
$name[2] = ‘Sarah’;
…
The ‘key’

Array keys
• Array keys can be strings as well as
numbers..
$surname[‘rob’] = ‘Tuley’;
$surname[‘si’] = ‘Lewis’;
• Notice the way that the key is specified, in
square brackets following the variable
name.

Working with arrays..
• Create Array (automatic keys):
$letters = array('a','b','c','d');
The array keys are automatically assigned by PHP
as 0, 1, 2, 3
i.e. $letters[1] has value ‘b’
• Create Array (explicit keys):
$letters = array(10=>’a’,13=>’b’);
i.e. $letters[13] has value ‘b’

Working with arrays…
• Create array (component by component):
$letters[10] = ‘a’;
$letters[13] = ‘b’;
• Access array component:
echo $letters[10];
// displays a
echo $letters[10].$letters[13];
// displays ab

Working with arrays…
Note that trying to echo an entire array will
not display the data. To print an entire
array to screen (for debug, for example)
use the function print_r instead.
echo $letters;
print_r($letters);

So..
We know we can:
1. Store things in named variables.
2. Use expressions to operate on the
contents of these variables.
3. Can compare variables..
How do we actually include logic in the
code such as ‘if this is bigger than
that, do this’?

Control Structures
• if, elseif, else
• while, do … while
• for, foreach
• switch
• break, continue, return
• require, include, require_once,
include_once

If …
• To do something depending on a
comparison, use an if statement.
if (comparison) {
expressions; // do if TRUE
}
• NB: Notice the curly brackets – these are
important!

If example
<?php
$a = 10;
$b = 13;
if ($a<$b) {
echo ‘a is smaller than b’;
}
?>

Extending IF statements
• It is possible to add extra optional clauses
to if statements..
if (comparison) {
expressions; // do if TRUE
} else {
expressions; // do otherwise
}

Extending If statements
if (comparison1) {
expressions;
} elseif (comparison2) {
expressions;
} else {
expressions;
}

An example..
$a = 10;
$b = 13;
if ($a<$b) {
echo ‘a is smaller than b’;
} elseif ($a==$b) {
echo ‘a is equal to b’;
} else {
echo ‘a is bigger than b’;
}

While loops
• Might want to do something repeatedly
while a comparison is true..
while (comparison) {
expressions;
}

Example
• Lets count to 10! Displays 1,2,3,4,5,..,10:
$i = 1;
while ($i <= 10) {
echo $i++;
}

Do .. While
• An alternative...
$i = 1;
do {
echo $i++;
} while ($i <= 10);

For loop
• Sometimes we want to loop around the same bit
of code a number of times.. Use a for loop.
• for (expr1; expr2; expr3) { statements; }
– expr1 evaluated/executed initially
– expr2 evaluated at beginning of each
iteration (Continues if TRUE)
– expr3 evaluated/executed at end of each
iteration

For loop example
• To count from 1 to 10:
for ($i=1; $i<=10; $i++) {
echo $i;
}
initialise
Continue if true
Execute at end of loop

Foreach loop
• A foreach loop is designed for arrays.
Often you want to loop through each item
in an array in turn..
$letters = array(‘a’,’b’,’c’);
foreach ($letters as $value) {
echo $value;
} // outputs a,b,c in turn

Foreach.. With keys
• Sometimes we want to use the array ‘key’
value too:
$letters = array(‘a’,’b’,’c’);
foreach ($letters as $key => $value) {
echo “array $key to $value”;
}

Switch statement
switch (expr) {
case (result1):
statements;
break;
case (result2):
statements;
break;
default:
statements;
}
• expr is evaluated
– Case corresponding to
result is executed
– Otherwise default case
is executed
• break
– Ensures next case isn’t
executed

Switch Example
switch ($name) {
case ‘Rob’:
echo ‘Your name is Rob’;
break;
case ‘Fred’:
echo ‘You are called Fred’;
break;
default:
echo ‘Not sure what your name is’;
}

break, continue, return
• break
– Ends execution of current for, foreach, do … while,
while or switch structure
– Option: Number of nested structures to break out of
• continue
– Skip rest of current loop
– Option: Number of nested loops to skip
• return
– Ends execution of current function/statement/script

Indentation..
• Code readability IS important – notice how
all the code inside a loop/control structure
is indented.
• Once you start writing nested control
loops, indentation is the only way to keep
track of your code!

require, include
• require('filename.ext')
– Includes and evaluates the specified file
– Error is fatal (will halt processing)
• include('filename.ext')
– Includes and evaluates the specified file
– Error is a warning (processing continues)
• require_once / include_once
– If already included won’t be included again

Code Re-use
• Often you will want to write a piece of code
and re-use it several times (maybe within
the same script, or maybe between
different scripts).
• Functions are a very nice way to
encapsulate such pieces of code..

Eh..? What?
• You have already used functions..
echo(‘text to display’);
Function NAME Function ARGUMENT

What is a function?
• A function takes some arguments (inputs)
and does something with them (echo, for
example, outputs the text input to the
user).
• As well as the inbuilt PHP functions, we
can define our own functions..

Definition vs. Calling
There are two distinct aspects to functions:
1. Definition: Before using a function, that
function must be defined – i.e. what
inputs does it need, and what does it do
with them?
2. Calling: When you call a function, you
actually execute the code in the function.

Function Definition
• A function accepts any number of input
arguments, and returns a SINGLE value.
function myfunction($arg1,$arg2,…,$argN)
{
statements;
return $return_value;
}

Example
• Function to join first and last names
together with a space..
function make_name($first,$last)
{
$fullname = $first.’ ‘.$last;
return $fullname;
}

Calling functions..
• Can be done anywhere..
myfunction($arg1,$arg2,…,$argN)
or
$answer = myfunction($arg1,$arg2,…,$argN)
e.g.
echo make_name(‘Rob’,’Tuley’);
// echoes ‘Rob Tuley’

Functions: Return Values
• Use return()
– Causes execution of function to cease
– Control returns to calling script
• To return multiple values
– Return an array
• If no value returned
– NULL

‘Scope’
• A function executes within its own little
protected bubble, or local scope.
• What does this mean? Its means that the
function can’t ‘see’ any of the variables
you have defined apart from those passed
in as arguments..
• Each new function call starts a clean slate
in terms of internal function variables.

In other words..
• Variables within a function
– Are local to that function
• Disappear when function execution ends
• Variables outside a function
– Are not available within the function
• Unless set as global
• Remembering variables
– Not stored between function calls
• Unless set as static

Global variables..
• To access a variable outside the ‘local’ scope of
a function, declare it as a global:
function add5toa()
{
global $a;
$a = $a + 5;
}
$a = 9;
add5toa();
echo $a; // 14

Static Variables
• Local function variable values are not saved
between function calls unless they are declared
as static:
function counter()
{
static $num = 0;
return ++$num;
}
echo counter(); // 1

Default Arguments
• Can specify a default value in the function
definition which is used only if no value is
passed to the function when called..
• Defaults must be specified last in the list
function myfunction($arg1,$arg2=‘blah’)…
function myfunction($arg1=‘blah’,$arg2)…

Passing References
• Pass a reference to a variable
– Not the actual variable
• Why?
– Enables a function to modify its arguments
• How?
– Use an ampersand in front of the variable
– &$variable

Review
• More PHP!
– Expressions
– Operators
– Control Structures
– Functions

03-forms.ppt.pptx

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