PHP or HTML Form Validation - php

Question

I want to validate an HTML form in either HTML or PHP. By validate, I mean ensuring there is at least 1 character of text entered into each of the 2 textboxes. And either only alpha numeric characters entered, or have something that ensures that any punctuation doesn't end up with "/" before it.
At the moment my form is made up of 2 php pages (copied below), and then posted to a txt file.
I'm either after some (very basic) instructions on how to do it, or suggestions on my script below.
//HTML
<form style="" method="post" action="addtopic2.php">
Topic:<input name="topic" id="topicbox" maxlength="100" type="text"><br>
Outline: <textarea input wrap="nowrap" rows="10" cols="120"
name="outline"></textarea>
<br><input name="submit" value="Submit" type="submit">
</form>
//HTML
<?php
$t = "Topic:";
$o = "Outline:";
$topic = $_POST['topic'];
$outline = $_POST['outline'];
$data = "$t $topic | $o $outline |\n";
$fh = fopen("users.txt", "a");
fwrite($fh, $data);
fclose($fh);
?>
//ATTEMPTED TO USE FOLLOWING, BUT DOESNT SEEM TO WORK WHEN INSERTING INTO EITHER PAGES.
<?php
if($_POST['Submit'] == "submit")
{
$errorMessage = "";
if(empty($_POST['topic']))
{
$errorMessage .= "<li>A topic needs to be entered</li>";
}
if(empty($_POST['outline']))
{
$errorMessage .= "<li>An outline needs to be entered</li>";
}
$vartopic = $_POST['formtopic'];
$varoutline = $_POST['formoutline'];
if(!empty($errorMessage))
{
echo("<p>There was an error with your form:</p>\n");
echo("<ul>" . $errorMessage . "</ul>\n");
}
}
?>
<?php
if (isset($_POST['topic']) && isset($_POST['outline'])) {
$topic = trim($_POST['topic']);
$outline = trim($_POST['outline']);
}
else {
echo '<p>Fill the form</p>';
}
?>

Answer 1

Try
$file = "users.txt";
$errorMessage = array ();
if ($_POST ['Submit'] == "submit") {
if (empty ( $_POST ['topic'] )) {
$errorMessage [] = "A topic needs to be entered<";
}
if (empty ( $_POST ['outline'] )) {
$errorMessage [] = "An outline needs to be entered";
}
if (count ( $errorMessage ) == 0) {
$data = $_POST ['topic'] . "|" . $_POST ['outline'] . "\n";
$fh = fopen ( $file, "a" );
fwrite ( $fh, $data );
fclose ( $fh );
} else {
print ("<p>There was an error with your form:</p>\n") ;
print ("<ul>") ;
foreach ( $errorMessage as $error ) {
print "<li>" . $error . "<li>";
}
print ("</ul>") ;
}
}
// To Read Your File
$content = file ( $file );
print ("<p>File Details</p>\n") ;
foreach ( $content as $info ) {
list ( $topic, $outline ) = explode ( "|", $info );
print ("<ul>") ;
print "<li>Topic: " . $topic . "<li>";
print "<li>Outline:" . $outline . "<li>";
print ("</ul>") ;
}

Answer 2

Try this (single file) solution:
<form style="" method="post">
Topic:<input name="topic" id="topicbox" maxlength="100" type="text" value='<?= $_REQUEST['topic'] ?>><br>
Outline: <textarea input wrap="nowrap" rows="10" cols="120" name="outline"><?= $_REQUEST['outline'] ?></textarea>
<p/>
<input name="submit" value="Submit" type="submit">
</form>
<?php
if ($_REQUEST['submit'] !== 'submit')
{
exit;
}
if ($_REQUEST['topic'] == '')
{
echo "<p>Missing Topic.</p>\n";
exit;
}
if ($_REQUEST['outline'] == '')
{
echo "<p>Missing Outline.</p>\n";
exit;
}
$t = "Topic:";
$o = "Outline:";
$topic = $_POST['topic'];
$outline = $_POST['outline'];
$data = "$t $topic | $o $outline |\n";
$fh = fopen("users.txt", "a");
fwrite($fh, $data);
fclose($fh);
?>