Here’s what worked best for me when trying to script this (in case anyone else comes across this like I did):
$ pecl -d php_suffix=5.6 install <package>
$ pecl uninstall -r <package>
$ pecl -d php_suffix=7.0 install <package>
$ pecl uninstall -r <package>
$ pecl -d php_suffix=7.1 install <package>
$ pecl uninstall -r <package>
The -d php_suffix=<version> piece allows you to set config values at run time vs pre-setting them with pecl config-set. The uninstall -r bit does not actually uninstall it (from the docs):
vagrant@homestead:~$ pecl help uninstall
pecl uninstall [options] [channel/]<package> ...
Uninstalls one or more PEAR packages. More than one package may be
specified at once. Prefix with channel name to uninstall from a
channel not in your default channel (pecl.php.net)
Options:
...
-r, --register-only
do not remove files, only register the packages as not installed
...
The uninstall line is necessary otherwise installing it will remove any previously installed version, even if it was for a different PHP version (ex: Installing an extension for PHP 7.0 would remove the 5.6 version if the package was still registered as installed).