$_POST not running for the form inside PHP script - php

Question

I was making a form inside a PHP script and when i tried to access a field
of form in the same script it was giving me error Undefined index
This is my code:
<?php
$query="SELECT * FROM `vendor_list`";
$query_run=mysql_query($query);
if(mysql_num_rows($query_run)>0)
{
echo '<form method="POST">';
echo 'Book name:<input type="text" name="book_name" size="40" maxlength="40"><br><br>';
echo 'Number Of Copies:<input type="text" size="5" name="num_copies" maxlength="2"><br><br>';
echo '<select name="vendor_email">';
while($query_row=mysql_fetch_assoc($query_run))
{
$laser=$query_row['vendor_name'];
$email=$query_row['email'];
echo "<option value='".$email."'>".$laser."</option>";
}
echo '</select><br>';
echo '<input type="submit" value="submit">';
echo '</form>';
}
else
{
echo 'No vendor to display';
}
echo $_POST['book_name'];

Answer 1

USE THIS:-
<?php
$query="SELECT * FROM `vendor_list`";
$query_run=mysql_query($query);
if(mysql_num_rows($query_run)>0)
{
echo '<form method="POST">';
echo 'Book name:<input type="text" name="book_name" size="40" maxlength="40"><br><br>';
echo 'Number Of Copies:<input type="text" size="5" name="num_copies" maxlength="2"><br><br>';
echo '<select name="vendor_email">';
while($query_row=mysql_fetch_assoc($query_run))
{
$laser=$query_row['vendor_name'];
$email=$query_row['email'];
echo "<option value='".$email."'>".$laser."</option>";
}
echo '</select><br>';
echo '<input type="submit" value="submit">';
echo '</form>';
}
else
{
echo 'No vendor to display';
}
if($_POST){
echo $_POST['book_name'];
}
?>

Answer 2

Try this
<?php
$query="SELECT * FROM `vendor_list`";
$query_run=mysql_query($query);
if(mysql_num_rows($query_run)>0)
{
?>
<form method="POST" action="">
Book name:<input type="text" name="book_name" size="40" maxlength="40"><br><br>
Number Of Copies:<input type="text" size="5" name="num_copies" maxlength="2"><br><br>
<select name="vendor_email">
<?php
while($query_row=mysql_fetch_assoc($query_run))
{
$laser=$query_row['vendor_name'];
$email=$query_row['email'];
echo "<option value='".$email."'>".$laser."</option>";
}
?>
</select><br>
<input type="submit" name="submit" value="submit">
</form>
<?php
}
else
{
echo 'No vendor to display';
}
if(isset($_POST["submit"]))){
echo $_POST['book_name'];
}
?>

Answer 3

The Clean Way
All the breaks you have in that code are a hot mess...
Tip When you are echoing too much HTML just wrap it in an if..else.. like this...
<?php
$query = "SELECT * FROM `vendor_list`";
$query_run = mysql_query($query);
?>
<?php if(mysql_num_rows($query_run)>0): ?>
<form method="POST">
<label for="book_name">Book name:</label>
<input type="text" name="book_name" id="book_name" size="40" maxlength="40">
<label for="book_name"Number Of Copies:</label>
<input type="text" size="5" name="num_copies" maxlength="2">
<select name="vendor_email">
<?php while($query_row=mysql_fetch_assoc($query_run)): ?>
<option value="<?=$query_row['email']?>"><?=$query_row['vendor_name']?></option>
<?php endwhile; ?>
</select>
<input type="submit" value="submit">
</form>
<?php else: ?>
<p>No vendor to display</p>
<?php endif; ?>
<?php if (isset($_POST['book_name'])) echo $_POST['book_name']; ?>

Answer 4

Using the below code this will also check if you have a form submission or not, unless this code is a cut/copy paste.. It looks like it will process sections when it should not.. eg the echo post..
Personally i myself will set the action="" to PHP_SELF as many years ago had issues with it, soon this will change once i start using HTML5 when its cross browser enough / older users update their browsers.
Example of processing or showing a post but not both.
echo $_POST['book_name'];
echo "POST Dump: " . print_r($_POST, true);
} else {
// No Form Submission, So we generate the form instead
// QUERY - data
$query = "SELECT * FROM 'vendor_list'";
$query_run = mysql_query($query);
if(mysql_num_rows($query_run)>0) {
// FORM - Name/#Copies
echo '<form method="POST" action="' . $_SERVER['PHP_SELF'] . '">';
echo 'Book name:<input type="text" name="book_name" size="40" maxlength="40"><br><br>';
echo 'Number Of Copies:<input type="text" size="5" name="num_copies" maxlength="2"><br><br>';
// FORM - Select Vendor
echo '<select name="vendor_email">';
while($query_row=mysql_fetch_assoc($query_run))
{
$laser=$query_row['vendor_name'];
$email=$query_row['email'];
echo "<option value='".$email."'>".$laser."</option>";
}
echo '</select><br>';
// FORM - Submit / Close Form
echo '<input type="submit" value="submit">';
echo '</form>';
} else {
echo 'No vendor to display';
}
}
?>
Or using a code that shows the form and processing any $_POST
<?php
// QUERY - data
$query = "SELECT * FROM 'vendor_list'";
$query_run = mysql_query($query);
if(mysql_num_rows($query_run)>0) {
// FORM - Name/#Copies
echo '<form method="POST" action="' . $_SERVER['PHP_SELF'] . '">';
echo 'Book name:<input type="text" name="book_name" size="40" maxlength="40"><br><br>';
echo 'Number Of Copies:<input type="text" size="5" name="num_copies" maxlength="2"><br><br>';
// FORM - Select Vendor
echo '<select name="vendor_email">';
while($query_row=mysql_fetch_assoc($query_run))
{
$laser=$query_row['vendor_name'];
$email=$query_row['email'];
echo "<option value='".$email."'>".$laser."</option>";
}
echo '</select><br>';
// FORM - Submit / Close Form
echo '<input type="submit" value="submit">';
echo '</form>';
} else {
echo 'No vendor to display';
}
if (isset($_POST['book_name'])) {
echo "<b>Displaying post data</b> <br />";
echo "Example book: " . $_POST['book_name'] . "<br />";
echo "POST Dump: <br /><pre>" . print_r($_POST, true) . "</pre>";
} else {
echo "Page has not been subitted yet, please select an item";
}
?>