PHP: in_array() 与 array_intersect() 的性能对比

Question

手动使用foreach迭代数组并使用in_array()检查needle是否出现，还是使用array_intersect()更快，效果更好？

- The Onin

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这篇文章可能对你有帮助：https://dev59.com/NcTCzogBFxS5KdRjKNWE - Mahdi Rashidi

Answer 1

基准测试

测试脚本

<?php
$numbers = range(32, 127);
$numbersLetters = array_map('chr', $numbers);

for (;;) {
    $numbersLetters = array_merge($numbersLetters, $numbersLetters);

    if (count($numbersLetters) > 10000) {
        break;
    }
}

$numbers = range(1, count($numbersLetters));

printf("Sample size: %d elements in 2 arrays (%d total) \n", count($numbers), count($numbers) + count($numbersLetters));
printf("Benchmarking speed in foreach + in_array() scenario... (this might take a while) ");

shuffle($numbers);
shuffle($numbersLetters);

$t1 = microtime(true);

foreach ($numbers as $number) {
    if (in_array($number, $numbersLetters)) {}
}

$t2 = microtime(true);

printf("DONE!\n");
printf("Time elapsed: %.5f \n", $t2 - $t1);

// =============================------------===============================

printf("Benchmarking speed with array_intersect...");

shuffle($numbers);
shuffle($numbersLetters);

$t1 = microtime(true);

array_intersect($numbers, $numbersLetters);

$t2 = microtime(true);

printf("DONE!\n");
printf("Time elapsed: %.5f \n", $t2 - $t1);

输出

Sample size: 12288 elements in 2 arrays (24576 total) 
Benchmarking speed in foreach + in_array() scenario... (this might take a while) DONE!
Time elapsed: 3.79213 
Benchmarking speed with array_intersect...DONE!
Time elapsed: 0.05765 

Fiddle: http://ideone.com/OZ2Idf

为什么array_intersect比foreach+in_array要快？

• 交集运算是在C代码中计算的，而不是在PHP中
• 在计算交集之前，Zend引擎内部会对数组进行排序，这样可以提高处理速度(为什么处理已排序的数组更快？)。

结论

array_intersect比foreach+in_array要快得多。

- The Onin

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在这里更新，包括 https://codedmemes.com/lib/best-performance-array-intersection/ 将是不错的。 - Rafał Łyczkowski

快进到PHP 8.2，差异仍然是一个数量级的小幅增加。 foreach + in_array() ：5.11544，array_intersect：0.01294。 - Markus AO