Online PHP editor | rfc for 2kHVL

@ 2026-04-09T23:18:06Z

<?php


// Source - https://stackoverflow.com/a/9276284
// Posted by kingmaple, modified by community. See post 'Timeline' for change history
// Retrieved 2026-04-08, License - CC BY-SA 4.0

// Source - https://stackoverflow.com/a/53203232
// Posted by slaszu, modified by community. See post 'Timeline' for change history
// Retrieved 2026-04-08, License - CC BY-SA 4.0

// ini_set('memory_limit', '2048M');

function formatBytes(int $bytes): string {
	$units = ['B', 'KB', 'MB', 'GB'];
	$i = 0;
	while ($bytes >= 1024 && $i < count($units) - 1) {
		$bytes /= 1024;
		$i++;
	}
	return sprintf("%.2f %s", $bytes, $units[$i]);
}

function benchmark(callable $fn, string $label): array {
	gc_collect_cycles();
	gc_mem_caches();
	memory_reset_peak_usage();
	$mem = -memory_get_peak_usage();
	$time = -hrtime(true);
	$fn();
	$time += hrtime(true);
	$mem += memory_get_peak_usage();
	return [
		'label' => $label,
		'time_ms' => $time / 1e6,
		'mem_used' => $mem,
	];
}

function manual_intersect($arrayOne, $arrayTwo) {
	$index = array_flip($arrayOne);
	foreach ($arrayTwo as $value) {
		if (isset($index[$value])) {
			unset($index[$value]);
		}
	}
	foreach ($index as $value => $key) {
		unset($arrayOne[$key]);
	}
	return $arrayOne;
}

function flipped_intersect($arrayOne, $arrayTwo) {
	$index = array_flip($arrayOne);
	$second = array_flip($arrayTwo);
	$x = array_intersect_key($index, $second);
	return array_flip($x);
}


function runBenchmarks(int $n): void {
	echo "\n=== Array Intersection Benchmark for " . number_format($n) . " elements ===\n";

	// Generate test arrays
	$one = [];
	$two = [];
	for ($i = 0; $i < $n; $i++) {
		$one[] = rand(0, 1000000);
		$two[] = rand(0, 100000);
		$two[] = rand(0, 10000);
	}

	$one = array_unique($one);
	$two = array_unique($two);

	$results = [];


	$results[] = benchmark(
		fn() => $res = array_intersect($one, $two),
		'array_intersect()'
	);

	$results[] = benchmark(
		fn() => $res = manual_intersect($one, $two),
		'manual_intersect()'
	);


	$results[] = benchmark(
		fn() => $res = flipped_intersect($one, $two),
		'flipped_intersect()'
	);

	// --- Print Table ---
	echo str_repeat('-', 60) . "\n";
	printf("%-25s | %-14s | %-15s\n", 'Method', 'Time (ms)', 'Memory');
	echo str_repeat('-', 60) . "\n";

	foreach ($results as $r) {
		printf("%-25s | %11.3f ms | %15s\n",
			$r['label'],
			$r['time_ms'],
			formatBytes($r['mem_used'])
		);
	}
	echo str_repeat('-', 60) . "\n";
}

// Run for various sizes
foreach ([20, 20000, 200000] as $n) {
	runBenchmarks($n);
}

Output for git.master_jit: === Array Intersection Benchmark for 20 elements === ------------------------------------------------------------ Method | Time (ms) | Memory ------------------------------------------------------------ array_intersect() | 0.023 ms | 3.02 KB manual_intersect() | 0.004 ms | 1.98 KB flipped_intersect() | 0.002 ms | 3.97 KB ------------------------------------------------------------ === Array Intersection Benchmark for 20,000 elements === ------------------------------------------------------------ Method | Time (ms) | Memory ------------------------------------------------------------ array_intersect() | 29.733 ms | 1.88 MB manual_intersect() | 0.950 ms | 1.75 MB flipped_intersect() | 1.146 ms | 3.00 MB ------------------------------------------------------------ === Array Intersection Benchmark for 200,000 elements === Fatal error: Out of memory (allocated 31469568 bytes) (tried to allocate 4194312 bytes) in /in/2kHVL on line 73 Stack trace: #0 /in/2kHVL(73): array_unique(Array) #1 /in/2kHVL(112): runBenchmarks(200000) #2 {main} mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.
Output for git.master: === Array Intersection Benchmark for 20 elements === ------------------------------------------------------------ Method | Time (ms) | Memory ------------------------------------------------------------ array_intersect() | 0.025 ms | 3.02 KB manual_intersect() | 0.004 ms | 1.98 KB flipped_intersect() | 0.002 ms | 3.97 KB ------------------------------------------------------------ === Array Intersection Benchmark for 20,000 elements === ------------------------------------------------------------ Method | Time (ms) | Memory ------------------------------------------------------------ array_intersect() | 28.513 ms | 1.88 MB manual_intersect() | 0.946 ms | 1.75 MB flipped_intersect() | 1.060 ms | 2.55 MB ------------------------------------------------------------ === Array Intersection Benchmark for 200,000 elements === Fatal error: Out of memory (allocated 37756928 bytes) (tried to allocate 2097160 bytes) in /in/2kHVL on line 74 Stack trace: #0 /in/2kHVL(74): array_unique(Array) #1 /in/2kHVL(112): runBenchmarks(200000) #2 {main} mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.

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2022-12-01 RFC: Property hooks - included in PHP 8.4
2020-03-21 RFC: Is_Literal - declined
2020-12-04 Enumerations - included in PHP 8.1
2018-06-15 Typed Properties v2 - implemented in PHP 7.4
2016-08-12 Object typehint - included in PHP 7.2
2016-08-14 Arrow functions - withdrawn
2016-05-29 array_change_keys() - withdrawn
2016-04-19 Lexical scope support for anonymous classes - suspended
2016-04-17 Functional Interfaces - declined
2016-03-16 Typed Properties - superseded in favor of Typed Properties 2.0
2015-08-27 Callable Prototypes - declined
2015-05-01 Short Closures - declined / withdrawn in favor of Arrow Functions
2015-02-18 Scalar type hints v5 - included in PHP 7
2015-02-14 Union Types - declined
2013-09-22 Anonymous classes - included in PHP 7

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