require和require_once都是PHP函数，开发人员可以使用它们在某个特定的脚本中导入外部PHP文件。你可以根据应用程序的复杂度调用一次或若干次require_once/require。使用require（而不是require_once）可以提高应用程序的性能。
测试前准备：
创建4个空的类来模拟主脚本要使用的外部PHP文件脚本。
ClassA.php：
<?php class ClassA { }
ClassB.php：
<?php class ClassB { }
ClassC.php：
<?php class ClassC { }
ClassD.php：
<?php class ClassD { }
使用require_once导入外部文件：
index.php：
<?php require_once './ClassA.php'; require_once './ClassB.php'; require_once './ClassC.php'; require_once './ClassD.php'; echo "Only testing require_once";
重启服务器，使用ab压力测试工具模拟10000个请求，同一时间有5个并发请求。
ab.exe -c 5 -n 10000 http://www.demo.com/optimization/index.php
测试结果：
D:phpStudyApachein>ab.exe -c 5 -n 10000 http://www.demo.com/optimization/index.php This is ApacheBench, Version 2.3 <$Revision: 1748469 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking www.demo.com (be patient) Completed 1000 requests Completed 2000 requests Completed 3000 requests Completed 4000 requests Completed 5000 requests Completed 6000 requests Completed 7000 requests Completed 8000 requests Completed 9000 requests Completed 10000 requests Finished 10000 requests Server Software: Apache/2.4.23 Server Hostname: www.demo.com Server Port: 80 Document Path: /optimization/index.php Document Length: 25 bytes Concurrency Level: 5 Time taken for tests: 17.446 seconds Complete requests: 10000 Failed requests: 0 Total transferred: 2280000 bytes HTML transferred: 250000 bytes Requests per second: 573.20 [#/sec] (mean) Time per request: 8.723 [ms] (mean) Time per request: 1.745 [ms] (mean, across all concurrent requests) Transfer rate: 127.63 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 0 0 0.4 0 2 Processing: 2 8 90.4 4 2503 Waiting: 1 7 90.5 3 2503 Total: 2 8 90.4 4 2504 Percentage of the requests served within a certain time (ms) 50% 4 66% 5 75% 5 80% 5 90% 5 95% 5 98% 6 99% 6 100% 2504 (longest request)
使用ab工具测试require_once，可以看到相应时间是8.723ms，该脚本每秒支持573.20个请求。
使用require导入外部文件：
index_1.php：
<?php require './ClassA.php'; require './ClassB.php'; require './ClassC.php'; require './ClassD.php'; echo "Only testing require";
重启服务器，使用ab压力测试工具模拟10000个请求，同一时间有5个并发请求。
ab.exe -c 5 -n 10000 http://www.demo.com/optimization/index_1.php
测试结果：
D:phpStudyApachein>ab.exe -c 5 -n 10000 http://www.demo.com/optimization/index_1.php This is ApacheBench, Version 2.3 <$Revision: 1748469 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking www.demo.com (be patient) Completed 1000 requests Completed 2000 requests Completed 3000 requests Completed 4000 requests Completed 5000 requests Completed 6000 requests Completed 7000 requests Completed 8000 requests Completed 9000 requests Completed 10000 requests Finished 10000 requests Server Software: Apache/2.4.23 Server Hostname: www.demo.com Server Port: 80 Document Path: /optimization/index_1.php Document Length: 20 bytes Concurrency Level: 5 Time taken for tests: 17.207 seconds Complete requests: 10000 Failed requests: 0 Total transferred: 2230000 bytes HTML transferred: 200000 bytes Requests per second: 581.16 [#/sec] (mean) Time per request: 8.604 [ms] (mean) Time per request: 1.721 [ms] (mean, across all concurrent requests) Transfer rate: 126.56 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 0 0 0.4 0 21 Processing: 1 8 86.5 4 2320 Waiting: 1 7 86.5 3 2320 Total: 1 8 86.5 4 2320 Percentage of the requests served within a certain time (ms) 50% 4 66% 5 75% 5 80% 5 90% 5 95% 6 98% 7 99% 7 100% 2320 (longest request) D:phpStudyApachein>ab.exe -c 5 -n 10000 http://www.demo.com/optimization/index_1.php This is ApacheBench, Version 2.3 <$Revision: 1748469 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking www.demo.com (be patient) Completed 1000 requests Completed 2000 requests Completed 3000 requests Completed 4000 requests Completed 5000 requests Completed 6000 requests Completed 7000 requests Completed 8000 requests Completed 9000 requests Completed 10000 requests Finished 10000 requests
使用ab工具测试require，可以看到相应时间是8.604ms，该脚本每秒支持581.16个请求。