Superglobals as Concepts

Cookie Values

$_COOKIE represents small values that the browser can send with later requests.

remembered preference Cookies are often used for small preferences such as a display theme.

Cookie Values

themeInput
cookie_values.php
Replay: real traced execution (multi-file project)
<?php
$themeInput = "light";
$_COOKIE["theme"] = $themeInput;
$theme = $_COOKIE["theme"] ?? "light";
$background = match ($theme) {
    "dark" => "black",
    "contrast" => "yellow",
    default => "white",
};

echo "theme=" . $theme . "\n";
echo "background=" . $background . "\n";

<?php
$themeInput = "dark";
$_COOKIE["theme"] = $themeInput;
$theme = $_COOKIE["theme"] ?? "light";
$background = match ($theme) {
    "dark" => "black",
    "contrast" => "yellow",
    default => "white",
};

echo "theme=" . $theme . "\n";
echo "background=" . $background . "\n";

<?php
$themeInput = "contrast";
$_COOKIE["theme"] = $themeInput;
$theme = $_COOKIE["theme"] ?? "light";
$background = match ($theme) {
    "dark" => "black",
    "contrast" => "yellow",
    default => "white",
};

echo "theme=" . $theme . "\n";
echo "background=" . $background . "\n";

  1. $themeInput ← light, $_COOKIE["theme"] ← light, $theme ← light

    1<?php2$themeInput→ light = "light"; //@themeInput="dark", "contrast"3$_COOKIE["theme"]→ light = $themeInputlight;4$theme→ light = $_COOKIE["theme"]light ?? "light";5$background→ white = match ($themelight) {6    "dark" => "black",7    "contrast" => "yellow",8    default => "white",9};1011echo "theme=" . $themelight . "\n";12echo "background=" . $backgroundwhite . "\n";
    outputtheme=light
background=white
    values this stepArray$_COOKIE

  1. $themeInput ← dark, $_COOKIE["theme"] ← dark, $theme ← dark, $background ← black

    1<?php2$themeInput→ dark = "dark";3$_COOKIE["theme"]→ dark = $themeInputdark;4$theme→ dark = $_COOKIE["theme"]dark ?? "light";5$background→ black = match ($themedark) {6    "dark" => "black",7    "contrast" => "yellow",8    default => "white",9};1011echo "theme=" . $themedark . "\n";12echo "background=" . $backgroundblack . "\n";
    outputtheme=dark
background=black
    values this stepArray$_COOKIE

  1. $themeInput ← contrast, $_COOKIE["theme"] ← contrast, $theme ← contrast

    1<?php2$themeInput→ contrast = "contrast";3$_COOKIE["theme"]→ contrast = $themeInputcontrast;4$theme→ contrast = $_COOKIE["theme"]contrast ?? "light";5$background→ yellow = match ($themecontrast) {6    "dark" => "black",7    "contrast" => "yellow",8    default => "white",9};1011echo "theme=" . $themecontrast . "\n";12echo "background=" . $backgroundyellow . "\n";
    outputtheme=contrast
background=yellow
    values this stepArray$_COOKIE