README

Offline US ZIP code lookup for PHP. No API calls, no database: the data ships as plain PHP arrays, split into one file per 3-digit prefix, so a lookup loads only one small file (and OPcache keeps it).

• ZIP, ZIP+4 (94105-1234 or 941051234) → state (USPS code) and city. Covers the 50 states, DC, PR, VI, GU, AS and MP.
• State lists: UsState (50 states + DC) and UsAddressState (adds the territories).

Install

composer require wckd123/us-postal-codes

Use

use WckD123\UsPostalCodes\PostalCodeLookup;
use WckD123\UsPostalCodes\UsAddressState;

$lookup = new PostalCodeLookup();

$match = $lookup->find('94105-1234');
// ['state' => 'CA', 'city' => 'San Francisco']

UsAddressState::NAMES_BY_CODE[$match[PostalCodeLookup::STATE]]; // 'California'

$lookup->find('123456'); // null - malformed
$lookup->find('00000');  // null - unknown

find() returns null for malformed and unknown ZIPs. Pass a folder to the constructor to read your own data (same layout as data/), e.g. a fixture in tests.

Performance and OPcache

Each find() call loads the data file for the ZIP's first three digits (at most about 100 lines) with require. With OPcache on, that file is compiled once and later calls read it from shared memory, so lookups are cheap.

OPcache is on by default for web requests (PHP-FPM, Apache) but off by default on the command line. For CLI scripts or queue workers that look up many ZIPs, turn it on in php.ini:

opcache.enable_cli=1

Without it, every call re-parses its file: still correct, just slower for bulk lookups.

Regenerating the data

Run from a clone of this repo (not from vendor/):

composer install
mkdir -p /tmp/geonames && cd /tmp/geonames
for c in US PR VI GU AS MP; do curl -sSLO https://download.geonames.org/export/zip/$c.zip && unzip -o -q $c.zip -d $c; done
cd - && php bin/generate-postal-code-data.php /tmp/geonames

Licence

Code: MIT. Data: see data/NOTICE.md (GeoNames, CC BY 4.0 - attribution required).