PHP form handling Tutorial
PHP form handling is the thing which irritates you if you’re a beginner.
The most important thing to notice when dealing with
HTML forms and PHP is that any form element in an
HTML page will automatically be available to your
PHP scripts.
Example
The example below contains an
HTML form with two input fields and a submit button:
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<html>
<body>
<form action="welcome.php" method="post">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
</body>
</html>
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When a user fills out the form above and click on the
submit button, the form data is sent to a PHP file,
called “
welcome.php“:
“welcome.php” looks like this:
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<html>
<body>
Welcome <?php echo $_POST["fname"]; ?>!<br />
You are <?php echo $_POST["age"]; ?> years old.
</body>
</html>
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Output could be something like this
Welcome John!
You are 28 years old.
The PHP $_GET and $_POST functions will be explained in the next chapters.
Form Validation
User input should be validated on the browser whenever possible (by
client scripts). Browser validation is faster and reduces the server
load.
You should consider server validation if the user input will be inserted into a
database.
A good way to validate a form on the server is to post the form to
itself, instead of jumping to a different page. The user will then get
the error messages on the same page as the form. This makes it easier to
discover the error.
The built-in $_GET function is used to collect values in a form with method=”get”.
The $_GET Function
The built-in $_GET function is used to collect values from a form sent with method=”get”.
Information sent from a form with the GET method is visible to
everyone (it will be displayed in the browser’s address bar) and has
limits on the amount of information to send (max. 100 characters).
Example
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<form action="welcome.php" method="get">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
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When the user clicks the “Submit” button, the URL sent to the server could look something like this:
http://www.voidtricks.com/welcome.php?fname=Peter&age=37
The “
welcome.php” file can now use the $_GET function
to
collect form data (the names of the form fields will automatically be
the keys in the $_GET array):
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Welcome <?php echo $_GET["fname"]; ?>.<br />
You are <?php echo $_GET["age"]; ?> years old!
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When to use method=”get”?
When using method=”get” in HTML forms, all variable names and values are displayed in the URL.
Note: This method should not be used when sending passwords or other sensitive information!
However, because the variables are displayed in the URL, it is possible to bookmark the page. This can be useful in some cases.
Note: The get method is not suitable for large variable values; the value cannot exceed 100 characters.
The built-in $_POST function is used to collect values in a form with method=”post”
The $_POST Function
The built-in $_POST function is used to collect values from a form sent with method=”post”.
Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.
Note: However, there is an 8
Mb max size for the
POST method, by default (can be changed by setting the post_max_size in
the php.ini file).
Example
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<form action="welcome.php" method="post">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
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When the user clicks the “Submit” button, the URL will look like this:
http://www.voidtricks.com/welcome.php
The “welcome.php” file can now use the $_POST function to collect
form data (the names of the form fields will automatically be the keys
in the $_POST array):
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Welcome <?php echo $_POST["fname"]; ?>!<br />
You are <?php echo $_POST["age"]; ?> years old.
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When to use method=”post”?
Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.
However, because the variables are not displayed in the URL, it is not possible to bookmark the page.
The PHP $_REQUEST Function
The PHP built-in $_REQUEST function contains the contents of both $_GET, $_POST, and $_COOKIE.
The $_REQUEST function can be used to collect form data sent
with both the GET and POST methods.
Example
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Welcome <?php echo $_REQUEST["fname"]; ?>!<br />
You are <?php echo $_REQUEST["age"]; ?> years old.
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