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[2001-03-31 04:58 UTC] admin at room41 dot net
The script shown attempts to implement a linked list, but the problem is more general and occurs in many similar situations.
<?
$d1 = @new obj("one"); // Suppress the warning over the missing argument
$d2 = new obj("two", $d1);
$d3 = new obj("three", $d2);
$d4 = new obj("four", $d3);
$d5 = new obj("five", $d4);
// Dump what should be the entire linked list
$d1->dump();
print("<p>");
// Now to demonstrate the problem:
// No matter where you begin the dump() from, only the
// $this node and its immediate successor are printed.
$d2->dump(); print("<p>");
$d3->dump(); print("<p>");
class obj {
var $next;
var $name;
function &obj($name,&$prev) {
// Add each new object as the "next" pointer of the preceeding one
this->name = $name;
if ($prev) $prev->next = $this;
}
function dump() {
for ( $ptr = $this; $ptr; $ptr = $ptr->next) print($ptr->name . "<br>");
}
}
?>
It seems that when an object's data is manipulated by a different object - even as here, of the same class - the changes made to the object are lost when its context expires.
Configuration: Absolutely standard
Webserver: Apache and IIS ... same problem in both, and under cgi and as a module
Aggravation factor: Immense
Cheer chaps for an otherwise excellent language!
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Last updated: Wed Oct 29 09:00:01 2025 UTC |
Your example is wrong. You're copying object everywhere like it is christmas day. Here's the corrected example for your convenience: <? $d1 = &new obj("one"); // Suppress the warning over the missing argument $d2 = &new obj("two", $d1); $d3 = &new obj("three", $d2); $d4 = &new obj("four", $d3); $d5 = &new obj("five", $d4); // Dump what should be the entire linked list $d1->dump(); print("\n\n"); // Now to demonstrate the problem: // No matter where you begin the dump() from, only the // $this node and its immediate successor are printed. $d2->dump(); print("\n\n"); $d3->dump(); print("\n\n"); class obj { var $next; var $name; function &obj($name,&$prev) { // Add each new object as the "next" pointer of the preceeding one $this->name = $name; if ($prev) $prev->next = &$this; } function dump() { for ( $ptr = &$this; $ptr; $ptr = &$ptr->next) print($ptr->name . "\n"); } } ?> Even if this example uses '&' where not needed it's good that way because not even a single object gets copied by accident. Closed.