Conflict between internal Apache and Apache installed via Homebrew
I had the same problem on a Sierra system. I run:

which -a apachectl


outputted:

/usr/sbin/apachectl
/usr/local/bin/apachectl


to stop the apache by apple version:  sudo /usr/sbin/apachectl stop

To see the running processes: ps aux | grep httpd Outputted:

ibook             1359   0,0  0,0  2432804    768 s000  S+    4:13pm   0:00.00 grep httpd
_www              1014   0,0  0,0  2479412    836   ??  S     3:57pm   0:00.00 

/usr/sbin/httpd -k restart
root              1013   0,0  0,1  2479668   7544   ??  Ss    3:57pm   0:00.12 /usr/sbin/httpd -k restart


So to stop apache by apple: sudo /usr/sbin/httpd -k stop
And to check if it occurred: ps aux | grep httpd Outputted:

ibok             1375   0,0  0,0  2432804    776 s000  S+    4:14pm   0:00.00 grep httpd


To start the brew apache:

sudo /usr/local/bin/apachectl start


And to check if it's on:  ps aux | grep httpd outputted:

 ibook             1390   0,0  0,0  2432804    768 s000  S+    4:14pm   0:00.00 grep httpd
    _www              1387   0,0  0,0  2652596    780   ??  S     4:14pm   0:00.00 /usr/local/opt/httpd/bin/httpd -k start
    _www              1386   0,0  0,0  2652596    752   ??  S     4:14pm   0:00.00 /usr/local/opt/httpd/bin/httpd -k start
    _www              1385   0,0  0,0  2652596    756   ??  S     4:14pm   0:00.00 /usr/local/opt/httpd/bin/httpd -k start
    _www              1384   0,0  0,0  2652596    756   ??  S     4:14pm   0:00.00 /usr/local/opt/httpd/bin/httpd -k start
    _www              1383   0,0  0,0  2652596    744   ??  S     4:14pm   0:00.00 /usr/local/opt/httpd/bin/httpd -k start
    root              1382   0,0  0,1  2652596  10976   ??  Ss    4:14pm   0:00.03 /usr/local/opt/httpd/bin/httpd -k start


To see the running version of apache: httpd -V that outputted: 

Server version: Apache/2.4.28 (Unix)
Server built:   Oct 29 2017 19:28:54
Server's Module Magic Number: 20120211:68
Server loaded:  APR 1.5.2, APR-UTIL 1.5.4
Compiled using: APR 1.5.2, APR-UTIL 1.5.4
Architecture:   64-bit
Server MPM:     prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_FLOCK_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=256
 -D HTTPD_ROOT="/usr"
 -D SUEXEC_BIN="/usr/bin/suexec"
 -D DEFAULT_PIDLOG="/private/var/run/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="/private/etc/apache2/mime.types"
 -D SERVER_CONFIG_FILE="/private/etc/apache2/httpd.conf"


And that was the APPLE installed version (2.4.28) again! In stead of the brew 2.4.38.
I recognize the frustration.

But it turns out that the pages in the localhost url are served by the new apache!

To show the OSX apache version:

Terminal input: /usr/sbin/apachectl -v

Server version: Apache/2.4.28 (Unix)
Server built:   Oct 29 2017 19:28:54

And to see the brew version:

Terminal input: /usr/local/bin/apachectl -v

Server version: Apache/2.4.38 (Unix)
Server built:   Feb 10 2019 02:49:25

And for php: 
Just type in terminal : which -a php
My mac shows:

/usr/bin/php

/usr/local/bin/php

And to show the php versions just use this:

Terminal input: /usr/bin/php -v

shows the OSX build in version:
PHP 5.6.30 (cli) (built: Oct 29 2017 20:30:32)
Copyright © 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright © 1998-2016 Zend Technologies

And terminal input: /usr/local/bin/php -v

Will show the brew version:
PHP 7.3.2 (cli) (built: Feb 14 2019 10:09:47) ( NTS )
Copyright © 1997-2018 The PHP Group
Zend Engine v3.3.2, Copyright © 1998-2018 Zend Technologies
with Zend OPcache v7.3.2, Copyright © 1999-2018, by Zend Technologies