The global Keyword and $GLOBALS

If you really need a function to use a global variable, PHP gives you two tools.

1. The global keyword

Write global $name; inside the function. It links the local name to the global variable.

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<?php
$counter = 0;

function increase(): void
{
    global $counter;
    $counter++;
}

increase();
increase();

echo $counter;

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2. The $GLOBALS array

$GLOBALS is a built-in array that holds every global variable.

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<?php
$language = "PHP";

function show(): void
{
    echo $GLOBALS["language"];
}

show();

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PHP

Why you should avoid both

Global variables work, but they cause trouble in real projects.

• The function secretly depends on something outside it, so you cannot understand it by reading it alone.
• Any code can change the global, so bugs are hard to trace.
• Testing the function is harder.

Compare the two styles:

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<?php
// Hidden dependency
$rate = 0.18;
function priceWithTax(float $price): float
{
    global $rate;
    return $price * (1 + $rate);
}

// Clear dependency
function priceWithTax2(float $price, float $rate): float
{
    return $price * (1 + $rate);
}

echo priceWithTax(100) . "\n";
echo priceWithTax2(100, 0.18);

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Same result, but the second version tells you what it needs in its signature.