PHP unable to write to MySQL database - php

Question

I have gone over my code many many MANY times and added any missing brackets or semi-colons but still whenever I upload this code to my website and load the page I still get a completely blank screen. The code was from an O'Reilly book so I went and checked the website if there are any reported errors in the book but found nothing related to this particular example.
I don't feel like it's an issue with permissions because I think the page would at least report one of the errors I coded into it. Could it have to do with the versions of PHP or MySQL I am using? I was able to connect to the database in the past and query it but writing just isn't happening. I am at a complete loss at this point. All I want to do is write to my MySQL database and party :(
Here is the code:
<?php
require_once 'login.php';
// Create connection
$db_server = mysql_connect($db_hostname, $db_username, $db_password);
// Check connection
if (!$db_server) die("Unable to connect to MySQL: " . mysql_error());
mysql_select_db($db_database, $db_server)
or die("Unable to select database: " . mysql_error());
if (isset($_POST['delete']) && isset($_POST['avail']))
{
$avail = get_post('avail');
$query = DELETE FROM test WHERE avail='$avail';
if (!mysql_query($query, $db_server))
echo "DELETE failed: $query<br />" .
mysql_error() . "<br /><br />";
}
if (isset($_POST['id']) &&
isset($_POST['item_name']) &&
isset($_POST['avail']))
{
$id = get_post('id');
$item_name = get_post('item_name');
$avail = get_post('avail');
$query = "INSERT INTO test VALUES" .
"('$id','$item_name','$avail')";
if (!mysql_query($query, $db_server))
{echo "INSERT failed: $query<br />" .
mysql_error() . "<br /><br />";
}
}
?>
<form action="index.php" method="post"><pre>
Line Number <input type="text" name="id" />
Product Name <input type="text" name="item_name" />
Quantity Available <input type="text" name="avail" />
<input type="submit" value="ADD RECORD" />
</pre></form>
<?php
$query = "SELECT * FROM test";
$result = mysql_query($query);
if (!$result) die ("Database access failed: " . mysql_error());
$rows = mysql_num_rows($result);
for ($j = 0 ; $j < $rows ; ++$j)
{
$row = mysql_fetch_row($result);
?>
<pre>
Line Number $row[0]
Product Name $row[1]
Quantity Available $row[2]
</pre>
<form action="index.php" method="post">
<input type="hidden" name="delete" value="yes" />
<input type="hidden" name="avail" value="$row[2]" />
<input type="submit" name="DELETE RECORD" /></form>
<?php
}
mysql_close($db_server);
function get_post($var)
{
return mysql_real_escape_string($_POST[$var]);
}
?>

Answer 1

you have error in the delete statment , try out this code :
<?php
require_once 'login.php';
// Create connection
$db_server = mysql_connect($db_hostname, $db_username, $db_password);
// Check connection
if (!$db_server) die("Unable to connect to MySQL: " . mysql_error());
mysql_select_db($db_database, $db_server)
or die("Unable to select database: " . mysql_error());
if (isset($_POST['delete']) && isset($_POST['avail']))
{
$avail = get_post('avail');
$query = "DELETE FROM test WHERE avail='$avail'";
if (!mysql_query($query, $db_server))
echo "DELETE failed: $query<br />" .
mysql_error() . "<br /><br />";
}
if (isset($_POST['id']) &&
isset($_POST['item_name']) &&
isset($_POST['avail']))
{
$id = get_post('id');
$item_name = get_post('item_name');
$avail = get_post('avail');
$query = "INSERT INTO test VALUES" .
"('$id','$item_name','$avail')";
if (!mysql_query($query, $db_server))
{echo "INSERT failed: $query<br />" .
mysql_error() . "<br /><br />";
}
}
?>
<form action="index.php" method="post"><pre>
Line Number <input type="text" name="id" />
Product Name <input type="text" name="item_name" />
Quantity Available <input type="text" name="avail" />
<input type="submit" value="ADD RECORD" />
</pre></form>
<?php
$query = "SELECT * FROM test";
$result = mysql_query($query);
if (!$result) die ("Database access failed: " . mysql_error());
$rows = mysql_num_rows($result);
for ($j = 0 ; $j < $rows ; ++$j)
{
$row = mysql_fetch_row($result);
?>
<pre>
Line Number $row[0]
Product Name $row[1]
Quantity Available $row[2]
</pre>
<form action="index.php" method="post">
<input type="hidden" name="delete" value="yes" />
<input type="hidden" name="avail" value="$row[2]" />
<input type="submit" name="DELETE RECORD" /></form>
<?php
}
mysql_close($db_server);
function get_post($var)
{
return mysql_real_escape_string($_POST[$var]);
}
?>

Answer 2

If no errors are being displayed add the following to the top of your file, it will allow for errors to be shown:
error_reporting(E_ALL);
ini_set('display_errors', '1');

Answer 3

Please ensure that you are displaying errors.
ini_set("display_errors", "1");
You can also create a new page with just
phpinfo();
to check that PHP is running (and what PHP configuration you have).