unsetting a variable trouble

[hexhaminfo]

Hi,

I have an email script which looks to my database for relevant records and then emails the relevant people in a while statement.

Problem is the variables won't seem to unset < maybe it's the wrong function?

Here's a basic idea of the code I'm using

$query = "SELECT url FROM mytable WHERE id ='whatever'";

$result = mysql_query($query) ;

while($row=mysql_fetch_array($result)){

$url = $row['url'];

if (!$url)  {
$mailbody1 = "
<h3>1. You don't have a website?</h3>
";}

else { 
$mailbody2 = "
<h3>1. You have a website</h3>
";}	

$mailbody = $mailbody1.$mailbody2;

mail($to, $subject, $mailbody, $headers);

unset ($url);

}

The above works perfectly on the first loop after that it's like the variable result from the first loop still exists... I've try'd loads of similar methods none seem to work.

Senario A.

user id 1 -- does not have a url in database
user id 2 -- does have a url

The above code produces >

email
to user 1 = You don't have a website

email to user 2 = You don't have a website
You have a website

Hope that makes sense and I really hope someone can help.

Thanks in advance.

Lee.

[hexhaminfo]

• should read

The above code produces >

email
to user 1 = You don't have a website

email to user 2 = You don't have a website
You have a website

[sneakyimp]

First off, please use the code formatting tags -- it makes your code easier to read.

You don't need to unset $url. It gets reset at the beginning of each record's loop.

Why are you doing this?

$mailbody = $mailbody1.$mailbody2;

What happens is that you set $mailbody1 in the loop for the first record and then when you get to the second record, you set $mailbody2 and then concatenate it together with $mailbody1 which still has its value from the first loop iteration. Why not just set $mailbody ?

[hexhaminfo]

Thanks sneakyimp,

I had a suspicion it was down to that.

The reason I am doing that is because the if statements are in the middle of the body of the email - how else could I split it to allow for if else statements then rejoin it to send?

Thanks (really thank you so much) - Lee.

[sneakyimp]

i haven't seen all your code so I don't really know. The thing to keep in mind is that each iteration of your loop, there's a chance that any variables you refer to might still have a value from the previous iteration. You can get around this problem by setting vars to NULL or the empty string at the beginning of the loop.

In the example you gave, you could easily use $mailbody in both the if and else sections. If your actual code is different, you are going to have to stay on top of the logic -- this is a pretty fundamental coding skill.

[hexhaminfo]

think i was getting confused between the result and the answer.

unset-ing the multiple mailbody variables fixed it - I'd love to know how to do it cleaner if anyone can be bothered to explain.

I think I was presuming (wrongly) that all variables set in the loop stayed in the loop.

Thanks again sneakyimp

[hexhaminfo]

If it was an echo statement I'd have no problem, I just carnt get my head around statements in a single variable.

What's the best way to do it?

[sneakyimp]

[man]unset[/man]ting a variable destroys the variable and is a bit overkill for this. It tells PHP to destroy the variable entirely rather than just emptying it out. You could try setting string variables to the empty string at the beginning of the loop. As for a single var versus multiple vars, it all depends on what your logic is like. Sometimes it's easier to have a few vars, sometimes it's easier to have one. In your original code, two vars seemed kind of pointless.

An alternative to initializing vars to the empty string is to make sure you always set the var properly. This can be tricky if you have complicated if/else structures or case statements.

while($row = mysql_fetch_array($result)) {
  // initialize vars
  $email_part_1 = '';
  $email_part_2 = '';

  if ($blah) {
    $email_part_1 = 'Some elaborate email string';
  } else {
    // here's an example where you might add extra else statements to make sure the var is null
    // it can get tricky if your logic is elaborate
    $email_part_1 = '';
  }

  // note the !
  if (!$blah) {
    $email_part_2 = 'this is the other var getting set in its own if statement';
  } else {
    $email_part_2 = 'diddly doo doo';
  }

}

The best way to do it always depends on your logic. Unfortunately, there's no 'best way' for every circumstance. You'll just have to think about what you are doing -- every single time 😉

[hexhaminfo]

I'm sure I had try'd that maybe the fail was down to the double quotes?

Thanks so much. I've got **** loads to learn 🙂

[sneakyimp]

I doubt this particular problem was due to any quote-related issues.