Installing phpredis on Ubuntu 14.04 for PHP 7.1 - php

Question

My php -v
PHP 7.1.15-1+ubuntu14.04.1+deb.sury.org+2 (cli) (built: Mar 6 2018
11:51:39) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine
v3.1.0, Copyright (c) 1998-2018 Zend Technologies
with Xdebug v2.6.0, Copyright (c) 2002-2018, by Derick Rethans
with Zend OPcache v7.1.15-1+ubuntu14.04.1+deb.sury.org+2, Copyright (c) 1999-2018, by Zend Technologies
I have tried both the pecl way
sudo pecl install redis
sudo service php7.1-fpm restart
And the manual way from https://github.com/phpredis/phpredis
phpize
./configure [--enable-redis-igbinary]
make && make install
I made sure to put
extension=/usr/lib/php/20170718/redis.so
into the php.ini file as shown when I run echo phpinfo();
e.g.
/etc/php/7.1/cli/php.ini
When I run the inbuilt web server I get
PHP Warning: PHP Startup: Unable to load dynamic library
'/usr/lib/php/20170718/redis.so' - /usr/lib/php/20170718/redis.so:
undefined symbol: zend_empty_string in Unknown on line 0
Strangely PHPStorm autocompletes the PHP Redis class, so
$redis = new \Redis();
$redis->connect('127.0.0.1', 6379);
I can click into the Redis class and see it is the correct one.
I wonder if it is a version difference? Maybe because I am using 32-bit?
Another strange thing is, if I just put
extension=redis.so
in php.ini, it seems to be looking for an older build
PHP Startup: Unable to load dynamic library
'/usr/lib/php/20160303/redis.so' - /usr/lib/php/20160303/redis.so:
cannot open shared object file: No such file or directory in Unknown
on line 0
When I run
sudo apt-get install php-redis
it installs and means that no start up error shows, but the web page still shows a
Class 'Redis' not found
One other thing I notice is that in Apache, there is no error, and the class is found. But when I run php's inbuilt web server, the not found error shows up.

Answer 1

May you just need to install this using a ppa package like:
sudo apt-get install php7.1-redis

Answer 2

Ok so I noticed that phpinfo showed
PHP API 20160303
which means that the earlier error makes sense. The PHP version of the web server is 7.1, however, when running the phpredis phpize it shows the one for 7.2.
So I just made sure to remove php7.2-dev and re-install php7.1 via apt-get, then re-run the github repo steps above.