两种实现方式，一个是 Unicode 码方式，一个是 if…else…
还有一个方式是把 Unicode 码拼接成这种 JSON，然后 json_decode 解析?
{“country_code”:”\ud83c\uddfa\ud83c\uddf8″}
<?php
function countryCodeEmoji($str) {
if(strlen($str) != 2) return $str;
$str = strtoupper($str);
return mb_convert_encoding( '&#' . ( 127397 + ord( $str[0] ) ) . ';', 'UTF-8', 'HTML-ENTITIES')
. mb_convert_encoding( '&#' . ( 127397 + ord( $str[1] ) ) . ';', 'UTF-8', 'HTML-ENTITIES');
}
echo countryCodeEmoji('cn');来源：https://nick.blog/2018/07/27/php-display-country-flag-emoji-from-iso-3166-1-alpha-2-country-codes/
function getFlags($code){
$code = strtoupper($code);
if($code == 'AD') return '??';
if($code == 'AE') return '??';
if($code == 'AF') return '??';
if($code == 'AG') return '??';
if($code == 'AI') return '??';
if($code == 'AL') return '??';
if($code == 'AM') return '??';
if($code == 'AO') return '??';
if($code == 'AQ') return '??';
if($code == 'AR') return '??';
if($code == 'AS') return '??';
if($code == 'AT') return '??';
if($code == 'AU') return '??';
if($code == 'AW') return '??';
if($code == 'AX') return '??';
if($code == 'AZ') return '??';
if($code == 'BA') return '??';
if($code == 'BB') return '??';
if($code == 'BD') return '??';
if($code == 'BE') return '??';
if($code == 'BF') return '??';
if($code == 'BG') return '??';
if($code == 'BH') return '??';
if($code == 'BI') return '??';
if($code == 'BJ') return '??';
if($code == 'BL') return '??';
if($code == 'BM') return '??';
if($code == 'BN') return '??';
if($code == 'BO') return '??';
if($code == 'BQ') return '??';
if($code == 'BR') return '??';
if($code == 'BS') return '??';
if($code == 'BT') return '??';
if($code == 'BV') return '??';
if($code == 'BW') return '??';
if($code == 'BY') return '??';
if($code == 'BZ') return '??';
if($code == 'CA') return '??';
if($code == 'CC') return '??';
if($code == 'CD') return '??';
if($code == 'CF') return '??';
if($code == 'CG') return '??';
if($code == 'CH') return '??';
if($code == 'CI') return '??';
if($code == 'CK') return '??';
if($code == 'CL') return '??';
if($code == 'CM') return '??';
if($code == 'CN') return '??';
if($code == 'CO') return '??';
if($code == 'CR') return '??';
if($code == 'CU') return '??';
if($code == 'CV') return '??';
if($code == 'CW') return '??';
if($code == 'CX') return '??';
if($code == 'CY') return '??';
if($code == 'CZ') return '??';
if($code == 'DE') return '??';
if($code == 'DJ') return '??';
if($code == 'DK') return '??';
if($code == 'DM') return '??';
if($code == 'DO') return '??';
if($code == 'DZ') return '??';
if($code == 'EC') return '??';
if($code == 'EE') return '??';
if($code == 'EG') return '??';
if($code == 'EH') return '??';
if($code == 'ER') return '??';
if($code == 'ES') return '??';
if($code == 'ET') return '??';
if($code == 'FI') return '??';
if($code == 'FJ') return '??';
if($code == 'FK') return '??';
if($code == 'FM') return '??';
if($code == 'FO') return '??';
if($code == 'FR') return '??';
if($code == 'GA') return '??';
if($code == 'GB') return '??';
if($code == 'GD') return '??';
if($code == 'GE') return '??';
if($code == 'GF') return '??';
if($code == 'GG') return '??';
if($code == 'GH') return '??';
if($code == 'GI') return '??';
if($code == 'GL') return '??';
if($code == 'GM') return '??';
if($code == 'GN') return '??';
if($code == 'GP') return '??';
if($code == 'GQ') return '??';
if($code == 'GR') return '??';
if($code == 'GS') return '??';
if($code == 'GT') return '??';
if($code == 'GU') return '??';
if($code == 'GW') return '??';
if($code == 'GY') return '??';
if($code == 'HK') return '??';
if($code == 'HM') return '??';
if($code == 'HN') return '??';
if($code == 'HR') return '??';
if($code == 'HT') return '??';
if($code == 'HU') return '??';
if($code == 'ID') return '??';
if($code == 'IE') return '??';
if($code == 'IL') return '??';
if($code == 'IM') return '??';
if($code == 'IN') return '??';
if($code == 'IO') return '??';
if($code == 'IQ') return '??';
if($code == 'IR') return '??';
if($code == 'IS') return '??';
if($code == 'IT') return '??';
if($code == 'JE') return '??';
if($code == 'JM') return '??';
if($code == 'JO') return '??';
if($code == 'JP') return '??';
if($code == 'KE') return '??';
if($code == 'KG') return '??';
if($code == 'KH') return '??';
if($code == 'KI') return '??';
if($code == 'KM') return '??';
if($code == 'KN') return '??';
if($code == 'KP') return '??';
if($code == 'KR') return '??';
if($code == 'KW') return '??';
if($code == 'KY') return '??';
if($code == 'KZ') return '??';
if($code == 'LA') return '??';
if($code == 'LB') return '??';
if($code == 'LC') return '??';
if($code == 'LI') return '??';
if($code == 'LK') return '??';
if($code == 'LR') return '??';
if($code == 'LS') return '??';
if($code == 'LT') return '??';
if($code == 'LU') return '??';
if($code == 'LV') return '??';
if($code == 'LY') return '??';
if($code == 'MA') return '??';
if($code == 'MC') return '??';
if($code == 'MD') return '??';
if($code == 'ME') return '??';
if($code == 'MF') return '??';
if($code == 'MG') return '??';
if($code == 'MH') return '??';
if($code == 'MK') return '??';
if($code == 'ML') return '??';
if($code == 'MM') return '??';
if($code == 'MN') return '??';
if($code == 'MO') return '??';
if($code == 'MP') return '??';
if($code == 'MQ') return '??';
if($code == 'MR') return '??';
if($code == 'MS') return '??';
if($code == 'MT') return '??';
if($code == 'MU') return '??';
if($code == 'MV') return '??';
if($code == 'MW') return '??';
if($code == 'MX') return '??';
if($code == 'MY') return '??';
if($code == 'MZ') return '??';
if($code == 'NA') return '??';
if($code == 'NC') return '??';
if($code == 'NE') return '??';
if($code == 'NF') return '??';
if($code == 'NG') return '??';
if($code == 'NI') return '??';
if($code == 'NL') return '??';
if($code == 'NO') return '??';
if($code == 'NP') return '??';
if($code == 'NR') return '??';
if($code == 'NU') return '??';
if($code == 'NZ') return '??';
if($code == 'OM') return '??';
if($code == 'PA') return '??';
if($code == 'PE') return '??';
if($code == 'PF') return '??';
if($code == 'PG') return '??';
if($code == 'PH') return '??';
if($code == 'PK') return '??';
if($code == 'PL') return '??';
if($code == 'PM') return '??';
if($code == 'PN') return '??';
if($code == 'PR') return '??';
if($code == 'PS') return '??';
if($code == 'PT') return '??';
if($code == 'PW') return '??';
if($code == 'PY') return '??';
if($code == 'QA') return '??';
if($code == 'RE') return '??';
if($code == 'RO') return '??';
if($code == 'RS') return '??';
if($code == 'RU') return '??';
if($code == 'RW') return '??';
if($code == 'SA') return '??';
if($code == 'SB') return '??';
if($code == 'SC') return '??';
if($code == 'SD') return '??';
if($code == 'SE') return '??';
if($code == 'SG') return '??';
if($code == 'SH') return '??';
if($code == 'SI') return '??';
if($code == 'SJ') return '??';
if($code == 'SK') return '??';
if($code == 'SL') return '??';
if($code == 'SM') return '??';
if($code == 'SN') return '??';
if($code == 'SO') return '??';
if($code == 'SR') return '??';
if($code == 'SS') return '??';
if($code == 'ST') return '??';
if($code == 'SV') return '??';
if($code == 'SX') return '??';
if($code == 'SY') return '??';
if($code == 'SZ') return '??';
if($code == 'TC') return '??';
if($code == 'TD') return '??';
if($code == 'TF') return '??';
if($code == 'TG') return '??';
if($code == 'TH') return '??';
if($code == 'TJ') return '??';
if($code == 'TK') return '??';
if($code == 'TL') return '??';
if($code == 'TM') return '??';
if($code == 'TN') return '??';
if($code == 'TO') return '??';
if($code == 'TR') return '??';
if($code == 'TT') return '??';
if($code == 'TV') return '??';
if($code == 'TW') return '??';
if($code == 'TZ') return '??';
if($code == 'UA') return '??';
if($code == 'UG') return '??';
if($code == 'UM') return '??';
if($code == 'US') return '??';
if($code == 'UY') return '??';
if($code == 'UZ') return '??';
if($code == 'VA') return '??';
if($code == 'VC') return '??';
if($code == 'VE') return '??';
if($code == 'VG') return '??';
if($code == 'VI') return '??';
if($code == 'VN') return '??';
if($code == 'VU') return '??';
if($code == 'WF') return '??';
if($code == 'WS') return '??';
if($code == 'XK') return '??';
if($code == 'YE') return '??';
if($code == 'YT') return '??';
if($code == 'ZA') return '??';
if($code == 'ZM') return '??';
return '?';
}