my delete function isn't working

green917 · December 19, 2009

Hi all,

I have a basic table for the site I'm writing that has a delete function for each record that should delete the record from the database. When you click the "delete" button, it appears to executes the command but, when I return to the contents table via the link I coded in, the record I was attempting to delete is still there. I have a feeling I may be calling the variable incorrectly in the mysql query called $query. The code follows. Any help would be greatly appreciated. Thank you in advance.

<?php

include 'config.php';

if ($_POST['delete']) {
$query = "DELETE FROM recipes WHERE $id = '$id'";
$result = mysql_query($query,$link);

echo 'Recipe has been deleted';
echo '<br /><br /><a href="/hlgcon.php">Back to database contents</a>';
}
else{

$sql = "SELECT id,title FROM recipes ORDER BY title";
$result = mysql_query($sql,$link);

?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<link rel="stylesheet" href="concss.css" type="text/css">
</head>

<body>


<form name="recitem" action="<?php echo $PHP_SELF ?>" method="post">
<table width="650" border="1" cellpadding="2" cellspacing="1">
<tr><th width="100%" colspan="3" style="background-color:#cddf77;"><center>Recipes</center></th></tr>
<tr><th>id</th><th>title</th><th>delete?</th></tr>

<?php
while($row = mysql_fetch_array($result)) {
echo '<tr><td>'.$row['id'].'</td>';
echo '<td>'.$row['title'].'</td>';
echo '<td><center><input type="submit" name="delete" value="delete" /></center></td>';
echo '</tr>';
}
echo '<TR><td width="100%" height="30" valign="center" colspan="3"><center><a href="/hlgup.php"><img src="recipebtn.gif" border="0"></a></center></td></TR>'; 

mysql_close($link);

?>	
</table>
</form>

</body>
</html>
<?php
}
?>

PravinS · December 19, 2009

Your delete query is wrong, you have used $ in where condition for field name. Use below given query.


$query = "DELETE FROM recipes WHERE id = '$id'";

abazoskib · December 19, 2009

To add to that, you never even define $id.

green917 · December 19, 2009

Thanks for the help but, after changing the $query and defining $id as

$id = $row['id'];

prior to the aforementioned $query, the function still isn't working. Any more help you can provide me is greatly appreciated as, obviously, I'm rather new to this stuff.

if (isset ($_POST['delete'])) {

include 'config.php';

$id = $row['id'];

$query = 'DELETE FROM recipes WHERE id="$id"';
$result = mysql_query($query,$link);

echo 'Recipe has been deleted';
echo '<br /><br /><a href="/hlgcon.php">Back to database contents</a>';
}
else{

include 'config.php';

$sql = "SELECT id,title FROM recipes ORDER BY title";
$result = mysql_query($sql,$link);

?>

PravinS · December 19, 2009

How will you get $row['id']?

abazoskib · December 19, 2009

you need to pass the actual id in a hidden input. then define the variable in a way like $id = $_POST['hidden_id'] after the form is submitted

green917 · December 19, 2009

Sorry for not getting this but, I still can't get it to delete the record. I updated the code by inserting a hidden input named "hidden_id" and passed it in a variable before establishing $query. The code is below. Thanks for all of your help again

<?php


if (isset ($_POST['delete'])) {

include 'config.php';

$id = $_POST['hidden_id'];

$del = 'DELETE FROM recipes WHERE id="$id"';
$result = mysql_query($del,$link);

echo 'Recipe has been deleted';
echo '<br /><br /><a href="/hlgcon.php">Back to database contents</a>';
}
else{

include 'config.php';

$sql = "SELECT id,title FROM recipes ORDER BY title";
$result = mysql_query($sql,$link);

?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<link rel="stylesheet" href="concss.css" type="text/css">
</head>

<body>


<form name="recitem" action="<?php echo $PHP_SELF ?>" method="post">
<table width="650" border="1" cellpadding="2" cellspacing="1">
<tr><th width="100%" colspan="4" style="background-color:#cddf77;"><center>Recipes</center></th></tr>
<tr><th>id</th><th>title</th><th>delete?</th></tr>

<?php
while($row = mysql_fetch_array($result)) {
echo '<tr><td>'.$row['id'].'</td>';
echo '<td>'.$row['title'].'</td>';
echo '<td><center><input type="hidden" name="hidden_id" value="$row[id]" /><input type="submit" name="delete" value="delete" /></center></td>';
echo '</tr>';
}
echo '<TR><td width="100%" height="30" valign="center" colspan="4"><center><a href="/hlgup.php"><img src="recipebtn.gif" border="0"></a></center></td></TR>'; 

mysql_close($link);

?>	
</table>
</form>

</body>
</html>
<?php
}
?>

premiso · December 19, 2009

$del = 'DELETE FROM recipes WHERE id="$id"';

That is invalid SQL, in MySQL you must use the single quotes around data.

$del = "DELETE FROM recipes WHERE id='$id'";

Try that and see if it works.

mrMarcus · December 19, 2009

as well, you cannot encapsulate php variables in single-quotes .. well, you can, they just won't be parsed.

this line:

echo '<td><center><input type="hidden" name="hidden_id" value="$row[id]" /> ...

must concatenate like so:

echo '<td><center><input type="hidden" name="hidden_id" value="' . $row['id'] . '" />

abazoskib · December 19, 2009

as well, you cannot encapsulate php variables in single-quotes .. well, you can, they just won't be parsed.

this line:
echo '<td><center><input type="hidden" name="hidden_id" value="$row[id]" /> ...
must concatenate like so:
echo '<td><center><input type="hidden" name="hidden_id" value="' . $row['id'] . '" />

You should really not get into the habit of echo'ing HTML, but another way to do it which has recently become my favorite:

echo '<td><center><input type="hidden" name="hidden_id" value="{$row['id']}" />'

premiso · December 19, 2009

echo '<td><center><input type="hidden" name="hidden_id" value="{$row['id']}" />'

That code won't work because of the single quotes the { } will only be interepted inside of double quotes:

echo "<td><center><input type='hidden' name='hidden_id' value='{$row['id']}' >";

Would be the proper way.

mrMarcus · December 19, 2009

You should really not get into the habit of echo'ing HTML ...

and why is that?

George Botley · December 19, 2009

Well,

It really is upto personal preference - but I have had cases where it uses resources on a server whilst parsing and echoing the HTML.

My recommendation for any echoing would be something similar to this:

<?

while($row=mysql_fetch_array($query)) {
//SOME CODE HERE THAT GETS DATA

?>

//SEE BELOW

<? } ?>

You may write pure HTML in the middle section as you have escape the PHP tag... Rest assured, the browser will still parse the PHP and still think that the HTML is within the PHP. This way, you can run if statements and loops etc whilst writing HTML within them without worrying about escaping values.

If you had a variable that you wanted called within the HTML you were writing simply restart a PHP tag and echo the variable like so <? echo "$name"; ?> - this would then echo the previously set variable into the pure HTML..

mrMarcus · December 20, 2009

my apologies. i was being sarcastic.

the difference in processing time is near non-existent. you're talking hundredths, even thousandths of milliseconds on some pretty heavy scripts (just ran a loop @ 10,000 iterations, and while there was a difference, both executed in under 0.04 of a second).

abazoskib · December 20, 2009

You should really not get into the habit of echo'ing HTML ...

and why is that?

You waste time/resources doing it. A good example is when I put together a table on a webpage listing over 1000 rows from a mysql table. I quickly threw it together and echo'ed the HTML. It was so darn slow. I simply placed the HTML outside of the PHP blocks, and I noticed much better speed when loading the table. I don't have an official benchmark for it, but no one has complained since. Also, it makes debugging much harder. Keep HTML as HTML, and PHP as PHP. You'll thank yourself when you have to go back weeks later to fix a bug.

abazoskib · December 20, 2009

my apologies. i was being sarcastic.

the difference in processing time is near non-existent. you're talking hundredths, even thousandths of milliseconds on some pretty heavy scripts (just ran a loop @ 10,000 iterations, and while there was a difference, both executed in under 0.04 of a second).

Maybe, but I'm positive that when viewing a webpage, loading times are a lot faster when you do not echo full HTML. Like I said it was very noticeable for myself and others that use my website.

I just re-tested it, with the old and new versions of the page, and its remarkably faster when just echo'ing the values , and not full HTML code.

green917 · December 22, 2009

Thank you all so much for all of your help. This solved my issue and taught me some important syntax lessons about php I didn't know before. I really appreciate the help.

Green

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