PHP script to convert a text file of two letter state abbreviations into full text names. You can replace the $us_state_abbrev array with just about any one-dimensional array to convert whatever you want (countries, etc). You can also easily change this so that full state names are converted to two-state codes.

stateNameCoversion.php

<?php

/*
* Replace list.txt with the name of your file. The file should only include a list of two-letter state abbreviations, one on each line.
* Results printed to STDIO, so use pipes to dump to a file if you want to save the results or add a function to do the same thing (I was 
* using this for CLI use which is why a function isnt in here already)
*
* Josh Wieder
* https://consulting.joshwieder.net
*/

$txtFile = "list.txt";

$us_state_abbrev = array(
    'Alabama' => 'AL',
    'Alaska' => 'AK',
    'Arizona' => 'AZ',
    'Arkansas' => 'AR',
    'California' => 'CA',
    'Colorado' => 'CO',
    'Connecticut' => 'CT',
    'Delaware' => 'DE',
    'Florida' => 'FL',
    'Georgia' => 'GA',
    'Hawaii' => 'HI',
    'Idaho' => 'ID',
    'Illinois' => 'IL',
    'Indiana' => 'IN',
    'Iowa' => 'IA',
    'Kansas' => 'KS',
    'Kentucky' => 'KY',
    'Louisiana' => 'LA',
    'Maine' => 'ME',
    'Maryland' => 'MD',
    'Massachusetts' => 'MA',
    'Michigan' => 'MI',
    'Minnesota' => 'MN',
    'Mississippi' => 'MS',
    'Missouri' => 'MO',
    'Montana' => 'MT',
    'Nebraska' => 'NE',
    'Nevada' => 'NV',
    'New Hampshire' => 'NH',
    'New Jersey' => 'NJ',
    'New Mexico' => 'NM',
    'New York' => 'NY',
    'North Carolina' => 'NC',
    'North Dakota' => 'ND',
    'North Carolina' => 'NC',
    'North Dakota' => 'ND',
    'Ohio' => 'OH',
    'Oklahoma' => 'OK',
    'Oregon' => 'OR',
    'Pennsylvania' => 'PA',
    'Rhode Island' => 'RI',
    'South Carolina' => 'SC',
    'South Dakota' => 'SD',
    'Tennessee' => 'TN',
    'Texas' => 'TX',
    'Utah' => 'UT',
    'Vermont' => 'VT',
    'Virginia' => 'VA',
    'Washington' => 'WA',
    'West Virginia' => 'WV',
    'Wisconsin' => 'WI',
    'Wyoming' => 'WY',
);

$csvRowArray = readCSV($txtFile);

function readCSV($txtFile){
        if (file_exists($txtFile)) {
            $file_handle = fopen($txtFile, 'r');
            while (!feof($file_handle) ) {
                $line_of_text[] = fgetcsv($file_handle, 1024);
            }
            fclose($file_handle);
            $line_of_text = array_values($line_of_text);
            $line_of_text = array_filter( $line_of_text );
            return $line_of_text;
        } else {
            echo "\nText file does not exist.";
            die;
        }
}

    ob_start();
    ob_start();
    foreach($csvRowArray as $key => $csvRow) {
        $key = array_search($csvRow[0], $us_state_abbrev);
        print_r ($key);
        echo "\n";
    }

    exit(0);
?>