Send mail with PHP using msmtp
Look for sendmail_path option in your php.ini and edit like this:

sendmail_path = "/usr/bin/msmtp -C /path/to/your/config -t"
oppure
sendmail_path = "/usr/bin/msmtp -t"


test php code:  (anche da shell:  php -a)
<?php
mail("your@email.com", "Test email from PHP", "msmtp as sendmail for PHP");
?>