Collections with SPL

SPL Stack

SplStack removes the most recently pushed item first.

last in first out Stacks are useful when the latest item should be processed before earlier items.

SPL Stack

base
spl_stack.php
Replay: real traced execution (multi-file project)
<?php
$base = "draft";
$stack = new SplStack();
$stack->push($base);
$stack->push("review");
$top = $stack->pop();
$next = $stack->top();
$remaining = $stack->count();

echo "base=" . $base . "\n";
echo "top=" . $top . "\n";
echo "next=" . $next . "\n";
echo "remaining=" . $remaining . "\n";

<?php
$base = "note";
$stack = new SplStack();
$stack->push($base);
$stack->push("review");
$top = $stack->pop();
$next = $stack->top();
$remaining = $stack->count();

echo "base=" . $base . "\n";
echo "top=" . $top . "\n";
echo "next=" . $next . "\n";
echo "remaining=" . $remaining . "\n";

<?php
$base = "ticket";
$stack = new SplStack();
$stack->push($base);
$stack->push("review");
$top = $stack->pop();
$next = $stack->top();
$remaining = $stack->count();

echo "base=" . $base . "\n";
echo "top=" . $top . "\n";
echo "next=" . $next . "\n";
echo "remaining=" . $remaining . "\n";

  1. $base ← draft, $stack ← SplStack, $top ← review, $next ← draft

    1<?php2$base→ draft = "draft"; //@base="note", "ticket"3$stack→ SplStack = new SplStack();4$stackSplStack->push($basedraft);5$stackSplStack->push("review");6$top→ review = $stackSplStack->pop();7$next→ draft = $stackSplStack->top();8$remaining→ 1 = $stackSplStack->count();910echo "base=" . $basedraft . "\n";11echo "top=" . $topreview . "\n";12echo "next=" . $nextdraft . "\n";13echo "remaining=" . $remaining1 . "\n";
    outputbase=draft
top=review
next=draft
remaining=1

  1. $base ← note, $stack ← SplStack, $top ← review, $next ← note, $remaining ← 1

    1<?php2$base→ note = "note";3$stack→ SplStack = new SplStack();4$stackSplStack->push($basenote);5$stackSplStack->push("review");6$top→ review = $stackSplStack->pop();7$next→ note = $stackSplStack->top();8$remaining→ 1 = $stackSplStack->count();910echo "base=" . $basenote . "\n";11echo "top=" . $topreview . "\n";12echo "next=" . $nextnote . "\n";13echo "remaining=" . $remaining1 . "\n";
    outputbase=note
top=review
next=note
remaining=1

  1. $base ← ticket, $stack ← SplStack, $top ← review, $next ← ticket

    1<?php2$base→ ticket = "ticket";3$stack→ SplStack = new SplStack();4$stackSplStack->push($baseticket);5$stackSplStack->push("review");6$top→ review = $stackSplStack->pop();7$next→ ticket = $stackSplStack->top();8$remaining→ 1 = $stackSplStack->count();910echo "base=" . $baseticket . "\n";11echo "top=" . $topreview . "\n";12echo "next=" . $nextticket . "\n";13echo "remaining=" . $remaining1 . "\n";
    outputbase=ticket
top=review
next=ticket
remaining=1