SplFixedArray is a class in PHP's Standard PHP Library (SPL) that provides a more memory-efficient and faster alternative to regular PHP arrays when you're working with a large number of elements and know the size in advance.

// Create a fixed-size array with 1 million elements
$start = microtime(true);
$fixedArray = new SplFixedArray(1000000);
for ($i = 0; $i < 1000000; $i++) {
    $fixedArray[$i] = $i;
}
$end = microtime(true);
echo "SplFixedArray time: " . ($end - $start) . " seconds\n";

// Compare with a regular PHP array
$start = microtime(true);
$regularArray = [];
for ($i = 0; $i < 1000000; $i++) {
    $regularArray[$i] = $i;
}
$end = microtime(true);
echo "Regular array time: " . ($end - $start) . " seconds\n";