$variable

$Variable

$VARIABLE

// lowercase
$variable = "Value 1";

// PascalCase
$Variable = "Value 2";

// UPPERCASE
$VARIABLE = "Value 3";

echo $variable . "\n";
echo $Variable . "\n";
echo $VARIABLE . "\n";

function printGreeting() {
	print "Prints: Hello world!\n";
}
printGreeting();