PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

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threads expanded.The expanded variable is an associative array that contains the
postid of articles that will have their replies expanded.
The parameter expand, which tells the script which new threads to expand.
The parameter collapse, which tells the script which threads to collapse.
When you click a plus or minus symbol or the Expand or Collapse button, this action
recalls the index.php script with new parameters for expand or collapse.You use
expanded from page to page to track which threads should be expanded in any given view.
The index.php script begins by starting a session and adding the expanded variable
as a session variable if this has not already been done. After that, the script checks
whether it has been passed an expand or collapse parameter and modifies the
expanded array accordingly. Look at the code for the expand parameter:
if(isset($_GET['expand'])) {
if($_GET['expand'] == 'all') {
expand_all($_SESSION['expanded']);
} else {
$_SESSION['expanded'][$_GET['expand']] = true;
}
}
If you click on the Expand button, the function expand_all() is called to add all the
threads that have replies into the expanded array. (We look at this in a moment.)
If you try to expand a particular thread, you will be passed a postid via expand.You
therefore add a new entry to the expanded array to reflect this.
The expand_all() function is shown in Listing 31.3.
Listing 31.3 expand_all() Function from discussion_fns.php—Processes the
$expanded Array to Expand All the Threads in the Forum
function expand_all(&$expanded) {
// mark all threads with children as to be shown expanded
$conn = db_connect();
$query = "select postid from header where children = 1";
$result = $conn->query($query);
$num = $result->num_rows;
for($i = 0; $ifetch_row();
$expanded[$this_row[0]]=true;
}
}
This function runs a database query to work out which of the threads in the forum have
replies, as follows: