the best way to use phalcon is to use zephir.
cd /home/my user/
git clone https://github.com/phalcon/zephir.git zephir;
cd zephir;
./install -c
zephir //just to make sure its working it should print you some crap, if not source ~/.bashrc.
//then you can take a look at ll /etc/alternatives | grep "php"
// the idea is that when you type which php,php-config, phpize should be the php7 ones. So my php7 is located at /opt/php-7004
//so here is my grep
lrwxrwxrwx 1 root root 21 Jul 27 15:34 php -> /opt/php-7004/bin/php*
lrwxrwxrwx 1 root root 17 Feb 19 2015 php-cgi -> /usr/bin/php5-cgi*
lrwxrwxrwx 1 root root 28 Jul 27 15:34 php-config -> /opt/php-7004/bin/php-config*
lrwxrwxrwx 1 root root 24 Jul 27 15:34 phpize -> /opt/php-7004/bin/phpize*
//in order to replace a executable,
rm php
ln -s /MY VERY FULL PATH TO php7/bin/php /etc/alternatives/php
Once that done, cd zephir/parser;
make clean
phpize --clean;
git clone phalcon
cd phalcon;
zephir build --zendEngine=3
//this will automatically install the extension in your php7 dir in my case i have this is my php.ini
extension=/opt/php-7004/lib/php/extensions/no-debug-non-zts-20151012/phalcon.so
//service apache/nginx restart and that it.
keep in mind that replacing php in /etc/alternatives wil make php -v ( show you the php7 one ) if you ever need to use the php5 one, just replace the file again.
Alternative way is to modify your PATH, probably its easiest way. You can check google.
I havent try this with 3.0 but...
git clone https://github.com/phalcon/cphalcon
cd cphalcon/build/64bits # <OR> cd cphalcon/build/32bits
make clean
phpize --clean
$YOUR_PHP_INSTALLATION_PATH/bin/phpize # Example: /opt/php-5.6.15/bin/phpize
./configure --with-php-config=$YOUR_PHP_INSTALLATION_PATH/bin/php-config # Example: ./configure --with-php-config=/opt/php-5.6.15/bin/php-config
make && sudo make install
also check here https://phalcon.io/bg/download