[php]By my previous understanding, due to the order of execution of recursive functions, when it is called it does not go on to execute the remaining part of the code but creates a new instance of the function in memory, the execution of the rest part of the function occurs at the last instance when the base case is fulfilled. In that light the code snippet
$row++;
}
// call display on each of this node’s children
// note a node will only have children in its list if expanded
$num_children = sizeof($this->m_childlist);
for($i = 0; $i<$num_children; $i++)
{
$row = $this->m_childlist[$i]->display($row, $sublist);
}
return $row;
}
will create several instances of the display() function which display the tree, but only return $row at last instance which is in turn returns $row to the instance that calls it until it get to the first. But the writer of the book says the snippet of code sends $row from one call to the next and then the next. How is this possible when the return of $row occurs after the call to the recursive function. What am I getting wrong?
<?php
// functions for loading, contructing and
// displaying the tree are in this file
class treenode
{
// each node in the tree has member variables containing
// all the data for a post except the body of the message
var $m_postid;
var $m_title;
var $m_poster;
var $m_posted;
var $m_children;
var $m_childlist;
var $m_depth;
function treenode($postid, $title, $poster, $posted, $children,
$expand, $depth, $expanded, $sublist)
{
// the constructor sets up the member variables, but more
// importantly recursively creates lower parts of the tree
$this->m_postid = $postid;
$this->m_title = $title;
$this->m_poster = $poster;
$this->m_posted = $posted;
$this->m_children =$children;
$this->m_childlist = array();
$this->m_depth = $depth;
// we only care what is below this node if it
// has children and is marked to be expanded
// sublists are always expanded
if(($sublist||$expand) && $children)
{
$conn = db_connect();
$query = "select * from header where parent = $postid order by posted";
$result = mysql_query($query);
for ($count=0; $row = @mysql_fetch_array($result); $count++)
{
if($sublist||$expanded[ $row['postid'] ] == true)
$expand = true;
else
$expand = false;
$this->m_childlist[$count]= new treenode($row['postid'],$row['title'],
$row['poster'],$row['posted'],
$row['children'], $expand,
$depth+1, $expanded, $sublist);
}
}
}
function display($row, $sublist = false)
{
// as this is an object, it is responsible for displaying itself
// $row tells us what row of the display we are up to
// so we know what color it should be
// $sublist tells us whether we are on the main page
// or the message page. Message pages should have
// $sublist = true.
// On a sublist, all messages are expanded and there are
// no "+" or "-" symbols.
// if this is the empty root node skip displaying
if($this->m_depth>-1)
{
//color alternate rows
echo '
';
else
echo '#ffffff">';
// indent replies to the depth of nesting
for($i = 0; $i<$this->m_depth; $i++)
{
echo '![]() ';
}
// display + or - or a spacer
if ( !$sublist && $this->m_children && sizeof($this->m_childlist))
// we're on the main page, have some children, and they're expanded
{
// we are expanded - offer button to collapse
echo '![Collapse Thread]() ';
}
else if(!$sublist && $this->m_children)
{
// we are collapsed - offer button to expand
echo '![Expand Thread]() ';
}
else
{
// we have no children, or are in a sublist, do not give button
echo '![]() ';
}
echo " m_postid >m_postid'>$this->m_title -
$this->m_poster - ".reformat_date($this->m_posted).'';
echo ' |
';
// increment row counter to alternate colors
$row++;
}
// call display on each of this node's children
// note a node will only have children in its list if expanded
$num_children = sizeof($this->m_childlist);
for($i = 0; $i<$num_children; $i++)
{
$row = $this->m_childlist[$i]->display($row, $sublist);
}
return $row;
}
};
?>[/php]
