Set cURL to use local virtual hosts
EDIT: While this is currently accepted answer, readers might find this other answer by user John Hart more adapted to their needs. It uses an option which, according to user Ken, was introduced in version 7.21.3 (which was released in December 2010, i.e. after this initial answer).
In your edited question, you're using the URL as the host name, whereas it needs to be the host name only.
Try:
curl -H 'Host: project1.loc' http://127.0.0.1/something
where project1.loc is just the host name and 127.0.0.1 is the target IP address.
(If you're using curl from a library and not on the command line, make sure you don't put http:// in the Host header.)
Either use a real fully qualified domain name (like dev.yourdomain.com) that pointing to 127.0.0.1 or try editing the proper hosts file (usually /etc/hosts in *nix environments).
Actually, curl has an option explicitly for this: --resolve
Instead of curl -H 'Host: yada.com' http://127.0.0.1/something
use curl --resolve 'yada.com:80:127.0.0.1' http://yada.com/something
What's the difference, you ask?
Among others, this works with HTTPS. Assuming your local server has a certificate for yada.com, the first example above will fail because the yada.com certificate doesn't match the 127.0.0.1 hostname in the URL.
The second example works correctly with HTTPS.
In essence, passing a "Host" header via -H does hack your Host into the header set, but bypasses all of curl's host-specific intelligence. Using --resolve leverages all of the normal logic that applies, but simply pretends the DNS lookup returned the data in your command-line option. It works just like /etc/hosts should.
Note --resolve takes a port number, so for HTTPS you would use
curl --resolve 'yada.com:443:127.0.0.1' https://yada.com/something
For setting up virtual hosts on Apache http-servers that are not yet connected via DNS, I like to use:
curl -s --connect-to ::host-name: http://project1.loc/post.json
Where host-name ist the IP address or the DNS name of the machine on which the web-server is running. This also works well for https-Sites.