PHP Issue with deleting from MySQL - php

Question

I do have programming experience, but new to php. I do have an issue with an example I was doing from this tutorial. I looked over it millions of times, googled, ect ect. I don't have an idea why my code isnt working.
The purpose is to basically just test inserting and deleting in sql from php, using a button for Add Record and Delete Record. The Add record button works perfectly, but delete doesnt do a thing other than reload the page. Heres the code...
<?php // sqltest.php
require_once 'login.php';
$db_server = mysql_connect($db_hostname, $db_username, $db_password);
if (!$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['author']) &&
isset($_POST['title']) &&
isset($_POST['type']) &&
isset($_POST['year']) &&
isset($_POST['isbn']))
{
$author = get_post('author');
$title = get_post('title');
$type = get_post('type');
$year = get_post('year');
$isbn = get_post('isbn');
if (isset($_POST['delete']) && $isbn != "")
{
echo "worked!!!!!!!!!!!!!!";
$query = "DELETE FROM classics WHERE isbn='$isbn'";
$result = mysql_query($query) or die(mysql_error());
if(mysql_affected_rows($result) > 0) echo 'user deleted';
//if (!mysql_query($query, $db_server))
//echo "DELETE failed: $query" . mysql_error();
}
else
{
echo "nooooooooooooooooooo";
$query = "INSERT INTO classics VALUES" .
"('$author', '$title', '$type', '$year', '$isbn')";
if (!mysql_query($query, $db_server))
{
echo "INSERT failed: $query" . mysql_error();
}
}
}
echo <<<_END
<form action="sqltest.php" method="post"><pre>
Author <input type="text" name="author" />
Title <input type="text" name="title" />
Type <input type="text" name="type" />
Year <input type="text" name="year" />
ISBN <input type="text" name="isbn" />
<input type='submit' value='ADD RECORD' />
</pre></form>
_END;
$query = "SELECT * FROM classics";
$result = mysql_query($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);
echo <<<_END
<pre>
Author $row[0]
Title $row[1]
Type $row[2]
Year $row[3]
ISBN $row[4]
<form action="sqltest.php" method="post">
<input type="hidden" name="delete" value="yes" />
<input type="hidden" name='isbn' value="$row[4]" />
<input type='submit' value='DELETE RECORD' />
</form>
</pre>
_END;
}
mysql_close($db_server);
function get_post($var)
{
return mysql_real_escape_string($_POST[$var]);
}
?>
I have looked over this many times, still no idea why this won't work. Is it the for loop that is making this button not work? Note, you will see echo "worked!!!"; and in the else echo "noooooooo"; that was for me to test whether the button was being tested, yet nothing prints. So maybe i missed something in the button code itself? Also, no errors are printed, and my editor (and myself) have missed the syntax error (if thats the case).
The code for the delete button is at the end, before I closed the DB.
Thanks for your help in advance.

Answer 1

Your problem is your first if block.
You're checking for the presence of the posted variables author title type year isbn. Whereas in your delete code the only variables sent are delete and isbn. Therefore the first if block is completely missed (including the delete code).
You need to modify your first if to be if(isset($_POST)) { // a form has been posted. Then it should work.
Another way to do it:
if(isset($_POST['delete']) && isset($_POST['isbn']) && !empty($_POST['isbn'])){
//delete code here
}
if(isset($_POST['author']) && isset($_POST['title']) && isset....){
// insert code here
}
EDIT: rewritten code:
<?php // sqltest.php
// I don't know what's in here, so I've left it
require_once 'login.php';
$db_server = mysql_connect($db_hostname, $db_username, $db_password);
if (!$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))
{
if (isset($_POST['delete']) && !empty($_POST['isbn']))
{
echo "Deleting";
$query = "DELETE FROM classics WHERE isbn='".mysql_real_escape_string($_POST['isbn'])."'";
$result = mysql_query($query) or die(mysql_error());
if(mysql_affected_rows($result) > 0) echo 'user deleted';
}
else
{
echo "Inserting";
$query = "INSERT INTO classics VALUES ('".mysql_real_escape_string($_POST['author'])."', '".mysql_real_escape_string($_POST['title'])."', '".mysql_real_escape_string($_POST['type'])."', '".mysql_real_escape_string($_POST['year'])."', '".mysql_real_escape_string($_POST['isbn'])."')";
if (!mysql_query($query))
{
echo "INSERT failed: $query" . mysql_error();
}
}
}
// you don't need echo's here... just html
?>
<form action="sqltest.php" method="post">
<pre>
Author <input type="text" name="author" />
Title <input type="text" name="title" />
Type <input type="text" name="type" />
Year <input type="text" name="year" />
ISBN <input type="text" name="isbn" />
<input type='submit' value='ADD RECORD' />
</pre>
</form>
<?php
$query = "SELECT * FROM classics";
$result = mysql_query($query);
if (!$result) die ("Database access failed: " . mysql_error());
// a better way to do this:
while($row = mysql_fetch_array($result)){
?>
<pre>
Author <?php echo $row[0]; ?>
Title <?php echo $row[1]; ?>
Type <?php echo $row[2]; ?>
Year <?php echo $row[3]; ?>
ISBN <?php echo $row[4]; ?>
<form action="sqltest.php" method="post">
<input type="hidden" name="delete" value="yes" />
<input type="hidden" name='isbn' value="<?php echo $row[4]; ?>" />
<input type='submit' value='DELETE RECORD' />
</form>
</pre>
<?php
}
mysql_close($db_server);
?>

Answer 2

Verify the method you used in your form. Make sure it's POST like this:
Form action="yourpage.php" method="POST"
and in your code above, replace the following:
$author = get_post('author');
$title = get_post('title');
$type = get_post('type');
$year = get_post('year');
$isbn = get_post('isbn');
with
$author = $_POST['author'];
$title = $_POST['title'];
$type = $_POST['type'];
$year = $_POST['year'];
$isbn = $_POST['isbn'];
Finally, there is no need to check again if the $isbn is not null as you did it in your isset() method. So remove $isbn!="" in the if below:
if (isset($_POST['delete']) && $isbn != "")
{
}
becomes:
if (isset($_POST['delete']))
{
}
Since you are testing, checking if the user clicked the delete button is of less importance. So you can also remove it for a while and add it later because you are sure that, that code is accessible after clicking the delete button.

Answer 3

You have no form field named delete, so it is impossible for your delete code path to ever be taken.
I'm guessing you're tryign to use the value of the submit button to decide what to do? In that case, you're also missing a name attribute on the submit button - without that, it cannot submit any value with the form. You probably want:
<input type="submit" name="submit" value="DELETE RECORD" />
and then have
if (isset($_POST['submit']) && ($_POST['submit'] == 'DELETE RECORD')) {
...
}