我已经安装了 WAMP 3，这是 PHP 7 和 PHP 5.6.16 附带的 x64 位版本。
问题是，它仅适用于版本 7，但不适用于版本 5.6.16。
如果我使用的是版本 7，我可以很好地打开 localhost，如果我切换到版本 5.6，它会显示“无法访问此站点”。阿帕奇错误日志：
[Fri Jul 08 18:59:42.721292 2016] [mpm_winnt:notice] [pid 8776:tid 652] AH00428: Parent: child process 8788 exited with status 255 -- Restarting.
[Fri Jul 08 18:59:42.859839 2016] [auth_digest:notice] [pid 8776:tid 652] AH01757: generating secret for digest authentication ...
[Fri Jul 08 18:59:42.936418 2016] [mpm_winnt:notice] [pid 8776:tid 652] AH00455: Apache/2.4.17 (Win64) PHP/5.6.16 configured -- resuming normal operations
[Fri Jul 08 18:59:42.936418 2016] [mpm_winnt:notice] [pid 8776:tid 652] AH00456: Apache Lounge VC14 Server built: Oct 11 2015 11:49:07
[Fri Jul 08 18:59:42.936418 2016] [core:notice] [pid 8776:tid 652] AH00094: Command line: 'C:\\wamp64\\bin\\apache\\apache2.4.17\\bin\\httpd.exe -d C:/wamp64/bin/apache/apache2.4.17'
[Fri Jul 08 18:59:43.007482 2016] [mpm_winnt:notice] [pid 8776:tid 652] AH00418: Parent: Created child process 5336
[Fri Jul 08 18:59:43.647394 2016] [auth_digest:notice] [pid 5336:tid 420] AH01757: generating secret for digest authentication ...
[Fri Jul 08 18:59:43.728167 2016] [mpm_winnt:notice] [pid 5336:tid 420] AH00354: Child: Starting 64 worker threads.
[Fri Jul 08 18:59:45.162617 2016] [mpm_winnt:notice] [pid 8776:tid 652] AH00428: Parent: child process 5336 exited with status 255 -- Restarting.
[Fri Jul 08 18:59:45.368338 2016] [auth_digest:notice] [pid 8776:tid 652] AH01757: generating secret for digest authentication ...
[Fri Jul 08 18:59:45.436406 2016] [mpm_winnt:notice] [pid 8776:tid 652] AH00455: Apache/2.4.17 (Win64) PHP/5.6.16 configured -- resuming normal operations
[Fri Jul 08 18:59:45.436406 2016] [mpm_winnt:notice] [pid 8776:tid 652] AH00456: Apache Lounge VC14 Server built: Oct 11 2015 11:49:07
[Fri Jul 08 18:59:45.436406 2016] [core:notice] [pid 8776:tid 652] AH00094: Command line: 'C:\\wamp64\\bin\\apache\\apache2.4.17\\bin\\httpd.exe -d C:/wamp64/bin/apache/apache2.4.17'
[Fri Jul 08 18:59:45.534501 2016] [mpm_winnt:notice] [pid 8776:tid 652] AH00418: Parent: Created child process 7404
[Fri Jul 08 18:59:46.217823 2016] [auth_digest:notice] [pid 7404:tid 156] AH01757: generating secret for digest authentication ...
[Fri Jul 08 18:59:46.276887 2016] [mpm_winnt:notice] [pid 7404:tid 156] AH00354: Child: Starting 64 worker threads.
可能是什么原因？