test.php

<?php
// See https://x.com/PoeHaH/status/1875290205894164758

function run_times( callable $callback, int $runs ) {
	$start = microtime(true);
	for ($i = 0; $i < $runs; $i++) {
		$callback();
	}
	return microtime(true) - $start;
}

$dir = trailingslashit( get_template_directory() );

$tests = [
	'option_non_existent' => function() {
		get_option( 'this_option_does_not_exist_' . random_int( 0, PHP_INT_MAX ) );
	},
	'option_non_existent_same' => function() {
		get_option( 'this_option_does_not_exist' );
	},
	'clear_stats_alone' => function() {
		clearstatcache( true );
	},
	'is_file_exists_with_clear_stats' => function() use ( $dir ) {
		clearstatcache( true );
		is_file( $dir . 'style.css' );
	},
	'is_file_exists_without_clear_stats' => function() use ( $dir ) {
		is_file( $dir . 'style.css' );
	},
	'file_exists_with_clear_stats' => function() use ( $dir ) {
		clearstatcache( true );
		file_exists( $dir . 'style.css' );
	},
	'file_exists_without_clear_stats' => function() use ( $dir ) {
		file_exists( $dir . 'style.css' );
	},
	'is_file_exists_not_with_clear_stats' => function() use ( $dir ) {
		clearstatcache( true );
		is_file( $dir . 'style-not-exists.css' );
	},
];

$runs = array_map(
	function( $test ) {
		return run_times( $test, 10000 );
	},
	$tests
);

print_r( $runs );