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 Posted by John C. Frickson on 03/09/07 23:25 
On 2007-03-09 17:03, fishmonger1972@gmail.com wrote: 
> I'm a librarian trying to put a finishing touch on an online materials 
> catalog.  The line below seems to do nothing in my program.. And I 
> don't get any error messages.  So, I'm  very perplexed because it 
> doesn't work as I'd like. 
>  
> I'm trying to see if $book_review_url is defined.. then if it is I 
> want it to make 'Click here for reviews for $title' to be hyperlinked 
> by the url that is in the database in $book_review_url.  Any help 
> would be appreciated! 
>  
>  
> <?php if (defined($book_review_url)) echo "<a href=\"$book_review_url 
> \">Click here for reviews for $title on Amazon.com</a>"; ?> 
 
defined() only works for constants, not variables. 
 
If you know that the variable $book_review_url exists and you 
want to just check if it's not empty, use 
      if ($book_review_url != "") 
 
If you don't know if the variable even exists, use 
      if (exists($book_review_url) && $book_review_url != "")
 
  
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