PHP - Introduction to PHP Forms

Introduction to PHPIntroduction to PHP
FormsForms

Forms: how they workForms: 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 workHow 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 FormXHTML Form
• The form is enclosed in form tags..
<form action=“path/to/submit/page”
method=“get”>
<!–- form contents -->
</form>

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

Form fields: text inputForm 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 areaForm 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 downForm 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 downForm 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 buttonsForm 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 buttonsForm 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 boxesForm 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 boxesForm 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 FieldsHidden 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..Submit button..
• A submit button for the form can be created with
the code:
<input type="submit"
name="submit"
value="Submit" />

FieldsetFieldset
• 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…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 dataAccess 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..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..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.

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

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

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

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

Is it submitted?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
}

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PHP - Introduction to PHP Forms

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