Here is an example. Feel free to edit the code to fit your needs.
<?php
$to = "YOU@YOURSITE.COM";
if (!isset($_POST['submit'])) {
showForm();
} else { //form submitted
$error = 0;
if(empty($_POST['name'])) {
$error = 1;
$errstr[] = "Please enter a name";
}
if(!preg_match("/^(?:[\w\d]+\.?)+@(?:(?:[\w\d]\-?)+\.)+\w{2,4}$/", $_POST['email'])) {
$error = 1;
$errstr[] = "Please enter a valid email address";
}
if (empty($_POST['subject'])) {
$error = 1;
$errstr[] = "Please enter a subject";
}
if(empty($_POST['message']) || preg_match("/^enter your message here$/i", $_POST['message'])) {
$error = 1;
$errstr[] = "Please enter a message";
}
if ($error == 1) {
echo "<center>\n<font style=\"color: #FF0000\">\n";
foreach($errstr as $err) {
echo "<li> " . $err . "</li>\n";
}
echo "</font>\n</center>\n<br />\n\n";
showForm();
} else {
@mail($to, "Site Contact - " . $_POST['subject'],
"Drew,\nOn " . date("r") . ", " . $_POST['name'] . " " . $_POST['email'] .
" sent the following message.\nReason " .
$_POST['reason'] . "\n\n" . stripslashes($_POST['message']), "From: " . $_POST['email']);
echo "<center>\nThanks for contacting me. I'll try to get back to you as soon as I can. Thanks for
visiting my website. If I don't get back to you within one week, please fill out the form again.<br /><br />"
."Click <a href=\"#\" onclick=\"self.close()\">here</a> to close this window.";
}
} //else submitted
function showForm()
{
$_POST['message'] = @htmlspecialchars(@$_POST['message']);
echo <<<EOD
<form method="POST">
<table class="dl" cellpadding="5" cellspacing="1" width="95%" align="center">
<tr>
<td class="head" align="center" colspan="2">Contact Form</td>
</tr>
<tr>
<td class="body" align="left">Name</td>
<td class="body" align="center"><input type="text" name="name" value="{$_POST['name']}" /></td>
</tr>
<tr>
<td class="body" align="left">Email Address</td>
<td class="body" align="center"><input type="text" name="email" value="{$_POST['email']}" /></td>
</tr>
<tr>
<td class="body" align="left">Subject</td>
<td class="body" align="center"><input type="text" name="subject" value="{$_POST['subject']}" /></td>
</tr>
<tr>
<td class="body" align="left">Contact Reason</td>
<td class="body" align="center"><select name="reason">
<option value="Question" selected>Question</option>
<option value="Comment">Comment</option>
<option value="Suggestion">Suggestion</option>
<option value="Bug">Bug Report</option>
<option value="Other">Other</option>
</select>
</td>
</tr>
<tr>
<td class="body" align="center" colspan="2"><textarea name="message" rows="8" cols="50">{$_POST['message']}</textarea></td>
</tr>
<tr>
<td class="body" align="center" colspan="2"><input type="submit" name="submit" value="Send Form" /></td>
</tr>
</table>
</form>
EOD;
}
?>