The API explorers show success with no errors:

Input Parameters:
{"person":{"email":“[email protected]”,“first_name”:“Eric”,“last_name”:“BobsTest”,“phone”:“213-423-4234”,“party”:“O”,“sex”:“O”,“employer”:“unknown”,“registered_address”:{"address1":“1911 W. Test Street”,“address2”:“null”,“country_code”:“US”,“city”:“Fountain”,“state”:“CO”,“zip”:"80901"}}}

Response:
{
“person”: {
“birthdate”: null,
“city_district”: null,
“civicrm_id”: null,
“county_district”: null,
“county_file_id”: null,
“created_at”: “2014-06-16T17:30:54-04:00”,
“do_not_call”: false,
“do_not_contact”: false,
“dw_id”: null,
“email”: “[email protected]”,
“email_opt_in”: true,
“employer”: “unknown”,
“external_id”: null,
“federal_district”: null,
“fire_district”: null,
“first_name”: “Eric”,
“has_facebook”: false,
“id”: 1632,
“is_twitter_follower”: false,
“is_volunteer”: false,
“judicial_district”: null,
“labour_region”: null,
“last_name”: “Reid”,
“linkedin_id”: null,
“mobile”: null,
“mobile_opt_in”: true,
“nbec_guid”: null,
“ngp_id”: null,
“note”: null,
“occupation”: null,
“party”: “O”,
“pf_strat_id”: null,
“phone”: “213-423-4234”,
“precinct_id”: null,
“primary_address”: {
“address1”: “1912 W Test St”,
“address2”: “null”,
“address3”: null,
“city”: “Fountain”,
“state”: “CO”,
“country_code”: “US”,
“zip”: “80901”,
“lat”: null,
“lng”: null
},
“recruiter_id”: null,
“rnc_id”: null,
“rnc_regid”: null,
“salesforce_id”: null,
“school_district”: null,
“school_sub_district”: null,
“sex”: “O”,
“state_file_id”: null,
“state_lower_district”: null,
“state_upper_district”: null,
“support_level”: null,
“supranational_district”: null,
“tags”: [],
“twitter_id”: null,
“twitter_name”: null,
“updated_at”: “2014-06-16T17:30:54-04:00”,
“van_id”: null,
“village_district”: null,
“active_customer_expires_at”: null,
“active_customer_started_at”: null,
“author”: null,
“author_id”: null,
“auto_import_id”: null,
“availability”: null,
“banned_at”: null,
“billing_address”: null,
“bio”: null,
“call_status_id”: null,
“call_status_name”: null,
“capital_amount_in_cents”: 0,
“children_count”: 0,
“church”: null,
“city_sub_district”: null,
“closed_invoices_amount_in_cents”: null,
“closed_invoices_count”: null,
“contact_status_id”: null,
“contact_status_name”: null,
“could_vote_status”: null,
“demo”: null,
“donations_amount_in_cents”: 0,
“donations_amount_this_cycle_in_cents”: 0,
“donations_count”: 0,
“donations_count_this_cycle”: 0,
“donations_pledged_amount_in_cents”: 0,
“donations_raised_amount_in_cents”: 0,
“donations_raised_amount_this_cycle_in_cents”: 0,
“donations_raised_count”: 0,
“donations_raised_count_this_cycle”: 0,
“donations_to_raise_amount_in_cents”: 0,
“email1”: “[email protected]”,
“email1_is_bad”: false,
“email2”: null,
“email2_is_bad”: false,
“email3”: null,
“email3_is_bad”: false,
“email4”: null,
“email4_is_bad”: false,
“ethnicity”: null,
“facebook_address”: null,
“facebook_profile_url”: null,
“facebook_updated_at”: null,
“facebook_username”: null,
“fax_number”: null,
“federal_donotcall”: false,
“first_donated_at”: null,
“first_fundraised_at”: null,
“first_invoice_at”: null,
“first_prospect_at”: null,
“first_recruited_at”: null,
“first_supporter_at”: “2014-06-16T17:30:54-04:00”,
“first_volunteer_at”: null,
“full_name”: “Eric BobsTest”,
“home_address”: null,
“import_id”: null,
“inferred_party”: null,
“inferred_support_level”: null,
“invoice_payments_amount_in_cents”: null,
“invoice_payments_referred_amount_in_cents”: null,
“invoices_amount_in_cents”: null,
“invoices_count”: null,
“is_deceased”: false,
“is_donor”: false,
“is_fundraiser”: false,
“is_ignore_donation_limits”: false,
“is_leaderboardable”: true,
“is_mobile_bad”: false,
“is_possible_duplicate”: false,
“is_profile_private”: false,
“is_profile_searchable”: true,
“is_prospect”: false,
“is_supporter”: true,
“is_survey_question_private”: false,
“language”: null,
“last_call_id”: null,
“last_contacted_at”: null,
“last_contacted_by”: null,
“last_donated_at”: null,
“last_fundraised_at”: null,
“last_invoice_at”: null,
“last_rule_violation_at”: null,
“legal_name”: null,
“locale”: null,
“mailing_address”: null,
“marital_status”: null,
“media_market_name”: null,
“meetup_address”: null,
“membership_expires_at”: null,
“membership_level_name”: null,
“membership_started_at”: null,
“middle_name”: null,
“mobile_normalized”: null,
“nbec_precinct_code”: null,
“note_updated_at”: null,
“outstanding_invoices_amount_in_cents”: null,
“outstanding_invoices_count”: null,
“overdue_invoices_count”: null,
“page_slug”: null,
“parent”: null,
“parent_id”: null,
“party_member”: false,
“phone_normalized”: “2134234234”,
“phone_time”: null,
“precinct_code”: null,
“precinct_name”: null,
“prefix”: null,
“previous_party”: null,
“primary_email_id”: 1,
“priority_level”: null,
“priority_level_changed_at”: null,
“profile_content”: null,
“profile_content_html”: null,
“profile_headline”: null,
“received_capital_amount_in_cents”: 0,
“recruiter”: null,
“recruits_count”: 0,
“registered_address”: {
“address1”: “1912 W Bijou St”,
“address2”: “null”,
“address3”: null,
“city”: “Colorado Springs”,
“state”: “CO”,
“country_code”: “US”,
“zip”: “80904”,
“lat”: null,
“lng”: null
},
“registered_at”: null,
“religion”: null,
“rule_violations_count”: 0,
“spent_capital_amount_in_cents”: 0,
“submitted_address”: null,
“subnations”: [],
“suffix”: null,
“support_level_changed_at”: null,
“support_probability_score”: null,
“turnout_probability_score”: null,
“twitter_address”: null,
“twitter_description”: null,
“twitter_followers_count”: null,
“twitter_friends_count”: null,
“twitter_location”: null,
“twitter_login”: null,
“twitter_updated_at”: null,
“twitter_website”: null,
“unsubscribed_at”: null,
“user_submitted_address”: null,
“username”: null,
“warnings_count”: 0,
“website”: null,
“work_address”: null,
“work_phone_number”: null,
“state_senate”: null,
“state_house”: null,
“signed_petition”: null,
“state_leader”: null,
“district_captain”: null,
“california_state_assembly”: null,
“california_state_senate”: null,
“district_code”: null
},
“precinct”: null
}

Output from PHP script: Same Parameters.

array(3) {
[“result”]=>
array(3) {
[“code”]=>
string(18) “missing_parameters”
[“message”]=>
string(19) “Missing Parameters.”
[“parameters”]=>
array(1) {
⁰=>
string(6) “person”
}
}
[“code”]=>
int(400)
[“content_type”]=>
string(16) “application/json”
}