This PHP function will take a string of a country name and return the 2 letter country code found at https://www.iso.org/obp/ui/#search.

convert_country2code

function convert_country2code($name) {

	$name_lc = mb_strtolower($name, 'UTF-8');

	$COUNTRIES = array (
		"andorra" => "AD",
		"united arab emirates" => "AE",
		"uae" => "AE",
		"afghanista" => "AF",
		"antigua and barbuda" => "AG",
		"antigua" => "AG",
		"barbuda" => "AG",
		"anguilla" => "AI",
		"albania" => "AL",
		"armenia" => "AM",
		"netherlands antilles" => "AN",
		"angola" => "AO",
		"antarctica" => "AQ",
		"argentina" => "AR",
		"american samoa" => "AS",
		"austria" => "AT",
		"australia" => "AU",
		"aruba" => "AW",
		"Åland islands" => "AX",
		"�land islands" => "AX", //strtolower seems to handle the å oddly
		"åland islands" => "AX",
		"aland islands" => "AX",
		"azerbaijan" => "AZ",
		"bosnia" => "BA",
		"herzegovina" => "BA",
		"bosnia and herzegovina" => "BA",
		"barbados" => "BB",
		"bangladesh" => "BD",
		"belgium" => "BE",
		"burkina faso" => "BF",
		"bulgaria" => "BG",
		"bahrain" => "BH",
		"burundi" => "BI",
		"benin" => "BJ",
		"saint barthélemy" => "BL",
		"saint barthelemy" => "BL",
		"bermuda" => "BM",
		"brunei darussalam" => "BN",
		"bolivia" => "BO",
		"bolivia (plurinational state of)" => "BO",
		"british antarctic territory" => "BQ",
		"bonaire" => "BQ",
		"sint eustatius" => "BQ",
		"saba" => "BQ",
		"bonaire, sint eurstatius and saba" => "BQ",
		"brazil" => "BR",
		"brasil" => "BR",
		"bahamas" => "BS",
		"bahamas (the)" => "BS",
		"the bahamas" => "BS",
		"bahamas, the" => "BS",
		"bhutan" => "BT",
		"burma" => "BU",
		"bouvet island" => "BV",
		"botswana" => "BW",
		"byelorussian ssr" => "BY",
		"belarus" => "BY",
		"belize" => "BZ",
		"canada" => "CA",
		"cocos islands" => "CC",
		"cocos islands, the" => "CC",
		"keeling islands" => "CC",
		"keeling islands, the" => "CC",
		"cocos (keeling) islands (the)" => "CC",
		"congo" => "CD",
		"congo (the democratic republic of the)" => "CD",
		"congo, the democratic republic of the" => "CD",
		"switzerland" => "CH",
		"côte d'ivoire" => "CI",
		"cote d'ivoire" => "CI",
		"cote divoire" => "CI",
		"cook islands" => "CK",
		"cook islands, the" => "CK",
		"cook islands (the)" => "CK",
		"chile" => "CL",
		"cameroon" => "CM",
		"china" => "CN",
		"china, people's republic of" => "CN",
		"colombia" => "CO",
		"costa rica" => "CR",
		"czechoslovakia" => "CS",
		"serbia" => "CS",
		"montenegro" => "ME",
		"serbia and montenegro" => "CS",
		"canton islands" => "CT",
		"enderbury islands" => "CT",
		"canton and enderbury islands" => "CT",
		"cuba" => "CU",
		"cabo verde" => "CV",
		"curaçao" => "CW",
		"curacao" => "CW",
		"christmas island" => "CX",
		"cyprus" => "CY",
		"czech republic (the)" => "CZ",
		"czech republic, the" => "CZ",
		"the chzech republic" => "CZ",
		"czech republic" => "CZ",
		"german democratic republic" => "DD",
		"germany" => "DE",
		"djibouti" => "DJ",
		"denmark" => "DK",
		"dominica" => "DM",
		"dominican republic (the)" => "DO",
		"dominican republic, the" => "DO",
		"the dominican republic" => "DO",
		"dominican republic" => "DO",
		"dahomey" => "DY",
		"algeria" => "DZ",
		"ecuador" => "EC",
		"estonia" => "EE",
		"egypt" => "EG",
		"western sahara" => "EH",
		"eritrea" => "ER",
		"spain" => "ES",
		"ethiopia" => "ET",
		"finland" => "FI",
		"fiji" => "FJ",
		"falkland islands" => "FK",
		"the falkland islands" => "FK",
		"falkland islands (the)" => "FK",
		"falkland islands, the" => "FK",
		"falkland islands, the (malvinas)" => "FK",
		"falkland islands (malvinas)" => "FK",
		"micronesia" => "FM",
		"micronesia, federated states of" => "FM",
		"micronesia (federated states of" => "FM",
		"federated states of micronesia" => "FM",
		"faroe islands (the)" => "FO",
		"faroe islands, the" => "FO",
		"the faroe islands" => "FO",
		"faroe islands" => "FO",
		"french southern and antartic territories" => "FQ",
		"france" => "FR",
		"france, metropolitan" => "FX",
		"gabon" => "GA",
		"united kingdom" => "GB",
		"united kingdom of great britain" => "GB",
		"united kingdom of great britain and northern ireland" => "GB",
		"united kingdom of great britain and northern ireland (the)" => "GB",
		"united kingdom of great britain and northern ireland, the" => "GB",
		"the united kingdom of great britain and northern ireland" => "GB",
		"grenada" => "GD",
		"gilbert island" => "GE",
		"ellice island" => "GE",
		"gilbert and ellice islands" => "GE",
		"georgia" => "GE",
		"french guiana" => "GF",
		"guernsey" => "GG",
		"ghana" => "GH",
		"gibraltar" => "GI",
		"greenland" => "GL",
		"gambia" => "GM",
		"gambia (the)" => "GM",
		"gambia, the" => "GM",
		"guinea" => "GN",
		"guadaloupe" => "GP",
		"equatorial guinea" => "GQ",
		"greece" => "GR",
		"south georgia and the south sandwich islands" => "GS",
		"south sandwich islands" => "GS",
		"guatemala" => "GT",
		"guam" => "GU",
		"guinea-bissau" => "GW",
		"guyana" => "GY",
		"hong kong" => "HK",
		"heard island and mcdonald islands" => "HM",
		"honduras" => "HN",
		"croatia" => "HR",
		"haiti" => "HT",
		"hungary" => "HU",
		"upper volta" => "HV",
		"indonesia" => "ID",
		"ireland" => "IE",
		"israel" => "IL",
		"isle of man" => "IM",
		"india" => "IN",
		"british indian ocean territory" => "IO",
		"british indian ocean territory (the)" => "IO",
		"british indian ocean territory, the" => "IO",
		"iraq" => "IQ",
		"iran (islamic republic of)" => "IR",
		"iran, islamic republic of" => "IR",
		"iran" => "IR",
		"iceland" => "IS",
		"italy" => "IT",
		"jersey" => "JE",
		"jamaica" => "JM",
		"jordan" => "JO",
		"japan" => "JP",
		"johnston island" => "JT",
		"kenya" => "KE",
		"kyrgyzstan" => "KG",
		"cambodia" => "KH",
		"kiribati" => "KI",
		"comoros (the)" => "KM",
		"comoros, the" => "KM",
		"comoros" => "KM",
		"saint kitts" => "KN",
		"nevis" => "KN",
		"saint kitts and nevis" => "KN",
		"korea (the democratic people's republic of)" => "KP",
		"korea, the democratic people's republic of" => "KP",
		"korea, democratic people's republic of" => "KP",
		"korea, democratic people's republic" => "KP",
		"korea" => "KR",
		"korea (the republic of)" => "KR",
		"korea, the republic of" => "KR",
		"korea, republic of" => "KR",
		"korea, (republic of)" => "KR",
		"kuwait" => "KW",
		"cayman islands" => "KY",
		"cayman islands (the)" => "KY",
		"cayman islands, the" => "KY",
		"the cayman islands" => "KY",
		"kazakhstan" => "KZ",
		"lao people's democratic republic" => "LA",
		"lao people's democratic republic (the)" => "LA",
		"lao people's democratic republic, the" => "LA",
		"the lao people's democratic republic" => "LA",
		"lebanon" => "LB",
		"saint lucia" => "LC",
		"liechtenstein" => "LI",
		"sri lanka" => "LK",
		"liberia" => "LR",
		"lesotho" => "LS",
		"lithuania" => "LT",
		"luxembourg" => "LU",
		"latvia" => "LV",
		"libya" => "LY",
		"morocco" => "MA",
		"monaco" => "MC",
		"moldova" => "MD",
		"moldova (the republic of)" => "MD",
		"moldova, the republic of" => "MD",
		"moldova, (republic of)" => "MD",
		"moldova, republic of" => "MD",
		"saint martin" => "MF",
		"madagascar" => "MG",
		"marshall islands" => "MH",
		"marshall islands (the)" => "MH",
		"marshall islands, the" => "MH",
		"midway islands" => "MI",
		"macedonia" => "MK",
		"macedonia (the former yugoslav republic of)" => "MK",
		"macedonia (former yugoslav republic of)" => "MK",
		"macedonia (former yugoslav republic)" => "MK",
		"macedonia, the former yugoslav republic of" => "MK",
		"macedonia, the former yugoslav republic" => "MK",
		"macedonia, former yugoslav republic of" => "MK",
		"macedonia, former yugoslav republic" => "MK",
		"mali" => "ML",
		"myanmar" => "MM",
		"mongolia" => "MN",
		"macao" => "MO",
		"northern mariana islands" => "MP",
		"northern mariana islands (the)" => "MP",
		"northern mariana islands, the" => "MP",
		"martinique" => "MQ",
		"mauritania" => "MR",
		"montserrat" => "MS",
		"malta" => "MT",
		"mauritius" => "MU",
		"maldives" => "MV",
		"malawi" => "MW",
		"mexico" => "MX",
		"malaysia" => "MY",
		"mozambique" => "MZ",
		"namibia" => "NA",
		"new caledonia" => "NC",
		"niger" => "NE",
		"niger (the)" => "NE",
		"niger, the" => "NE",
		"norfolk island" => "NF",
		"nigeria" => "NG",
		"new hebrides" => "NH",
		"nicaragua" => "NI",
		"netherlands" => "NL",
		"netherlands (the)" => "NL",
		"netherlands, the" => "NL",
		"the netherlands" => "NL",
		"norway" => "NO",
		"nepal" => "NP",
		"dronning maud land" => "NQ",
		"nauru" => "NR",
		"neutral zone" => "NT",
		"niue" => "NU",
		"new zealand" => "NZ",
		"oman" => "OM",
		"panama" => "PA",
		"pacific islands" => "PC",
		"pacific islands (trust territory)" => "PC",
		"pacific islands, trust territory" => "PC",
		"peru" => "PE",
		"french polynesia" => "PF",
		"papua new guinea" => "PG",
		"philippines (the)" => "PH",
		"philippines, the" => "PH",
		"philippines" => "PH",
		"pakistan" => "PK",
		"poland" => "PL",
		"saint pierre and miquelon" => "PM",
		"pitcairn" => "PN",
		"puerto rico" => "PR",
		"palestine" => "PS",
		"palestine, state of" => "PS",
		"united states miscellaneous pacific islands" => "PU",
		"palau" => "PW",
		"paraguay" => "PY",
		"panama canal zone" => "PZ",
		"panama" => "PZ",
		"qatar" => "QA",
		"réunion" => "RE",
		"reunion" => "RE",
		"southern rhodesia" => "RH",
		"romania" => "RO",
		"serbia" => "RS",
		"russia" => "RU",
		"russian federation" => "RU",
		"russian federation, the" => "RU",
		"russian federation (the)" => "RU",
		"rwanda" => "RW",
		"saudi arabia" => "SA",
		"solomon islands" => "SB",
		"seychelles" => "SC",
		"sudan" => "SD",
		"sudan (the)" => "SD",
		"sudan, the" => "SD",
		"sweden" => "SE",
		"singapore" => "SG",
		"saint helena" => "SH",
		"saint helenda, ascension and tristan da cunha" => "SH",
		"slovenia" => "SI",
		"svalbard" => "SJ",
		"svalbard and jan mayen" => "SJ",
		"slovakia" => "SK",
		"sikkim" => "SK",
		"sierra leone" => "SL",
		"san marino" => "SM",
		"senegal" => "SN",
		"somalia" => "SO",
		"suriname" => "SR",
		"south sudan" => "SS",
		"sao tome and principe" => "ST",
		"ussr" => "SU",
		"el salvador" => "SV",
		"sint maarten" => "SX",
		"syrian arab republic" => "SY",
		"syria" => "SY",
		"swaziland" => "SZ",
		"turks and caicos islands" => "TC",
		"turks and caicos islands (the)" => "TC",
		"turks and caicos islands, the" => "TC",
		"chad" => "TD",
		"french southern territories" => "TF",
		"french southern territories (the)" => "TF",
		"french southern territories, the" => "TF",
		"togo" => "TG",
		"thailand" => "TH",
		"tajikistan" => "TJ",
		"tokelau" => "TK",
		"timor-leste" => "TL",
		"turkmenistan" => "TM",
		"tunisia" => "TN",
		"tonga" => "TO",
		"east timor" => "TP",
		"turkey" => "TR",
		"trinidad and tobago" => "TT",
		"tuvalu" => "TV",
		"taiwan" => "TW",
		"taiwan (province of china)" => "TW",
		"taiwan, province of china" => "TW",
		"tanzania" => "TZ",
		"tanzania, united republic of" => "TZ",
		"ukraine" => "UA",
		"uganda" => "UG",
		"united states minor outlying islands" => "UM",
		"united states" => "US",
		"united states of america" => "US",
		"united states of america, the" => "US",
		"united states of america (the)" => "US",
		"uruguay" => "UY",
		"uzbekistan" => "UZ",
		"holy see" => "VA",
		"holy see (the)" => "VA",
		"holy see, the" => "VA",
		"saint vincent" => "VC",
		"grenadines" => "VC",
		"saint vincent and the grenadines" => "VC",
		"viet-nam, democratic republic of" => "VD",
		"vietnam" => "VN",
		"viet nam" => "VN",
		"viet-nam" => "VN",
		"vietnam, socialist republic" => "VN",
		"vietnam, socialist republic of" => "VN",
		"vietnam (socialist republic)" => "VN",
		"vietnam (socialist republic of)" => "VN",
		"viet nam, socialist republic" => "VN",
		"venezuela" => "VE",
		"venezuela (bolivarian republic of)" => "VE",
		"venezuela (bolivarian republic)" => "VE",
		"venezuela, bolvarian republic of" => "VE",
		"venezuela, bolvarian republic" => "VE",
		"virgin islands (british)" => "VI",
		"virgin islands, british" => "VI",
		"virgin islands (u.s.)" => "VI",
		"virgin islands (us)" => "VI",
		"virgin islands, u.s." => "VI",
		"virgin islands, us" => "VI",
		"vanuatu" => "VU",
		"wallis and futuna" => "WF",
		"wake island" => "WK",
		"samoa" => "WS",
		"yemen, democratic" => "YD",
		"yemen" => "YE",
		"mayotte" => "YT",
		"yugoslavia" => "YU",
		"south africa" => "ZA",
		"zambia" => "ZM",
		"zaire" => "ZR",
		"zimbabwe" => "ZW"
		);

	if (isset($COUNTRIES[$name_lc])) {
		return $COUNTRIES[$name_lc];
	}

	return false;
}