This example shows how to validate form data and to redisplay the form highlighting fields that need to be changed.
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!--
Displaying error messages for forms
Author: Elena Machkasova
Last Modifed: 4/17/2008
-->
<?php
$name = $_POST["name"];
$email = $_POST["email"];
$submit = $_POST["submit"]; // to check if the user got here through a form
function display_form($style1 = "", $style2 = "", $name_value="",
$email_value = "") {
print "<form method=\"post\"
action=\"form_validation.php\">
<table style=\"border: none\">
<tr>
<td $style1>Enter your name:</td>
<td>
<input type = \"text\" name = \"name\" $name_value />
</td>
</tr>
<tr>
<td $style2>Enter your e-mail:</td>
<td>
<input type = \"text\" name = \"email\" $email_value />
</td>
</tr>
<tr>
<td>
<input type=\"submit\" name = \"submit\" value=\"submit\" />
</td>
</tr>
</table>
</form>";
}
?>
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
<title>
Displaying errors
</title>
</head>
<body>
<?php
$style1 = "";
$style2 = "";
$error_style = "style = \"color: red\"";
$message = "";
$name_value = "";
$email_value = "";
$errors = false;
if (!isset($submit)) {
display_form(); // display the form
}
else {
// start validation
if (!eregi("^[a-z ]+$", $name)) {
$style1 = $error_style;
$message = $message."The name is empty or has illegal characters<br/>";
$errors = true;
} else {
$name_value = "value = \"$name\"";
}
if (!eregi("^([a-z0-9]+)@([a-z._]+)$", $email)) {
$style2 = $error_style;
$message = $message."The e-mail is empty or has illegal characters<br/>";
$errors = true;
} else {
$email_value = "value = \"$email\"";
}
if (!$errors) {
print "Thank you, $name, for submitting your information!<br/>\n";
} else {
// priniting the form
display_form($style1, $style2, $name_value, $email_value);
// printing the error message
print "<p $error_style>$message You need to resubmit the form</p>";
}
}
?>
</body>
</html>
http://rynite.morris.umn.edu/~elenam/1101_spring08/forms/form_validation.php