PHP function to verify ID number

function validation_filter_id_card($id_card){
 if(strlen($id_card)==18){
 return idcard_checksum18($id_card);
 }elseif((strlen($id_card)==15)){
 $id_card=idcard_15to18($id_card);
 return idcard_checksum18($id_card);
 }else{
 return false;
 }
}
// Calculate the ID card verification code, according to the national standard GB 11643-1999
function idcard_verify_number( $idcard_base){
 if(strlen($idcard_base)!=17){
 return false;
 }
 //Weighting factor
 $factor=array(7,9,10,5,8,4,2,1, 6,3,7,9,10,5,8,4,2);
 //Corresponding value of the check code
 $verify_number_list=array('1','0','X','9',' 8','7','6','5','4','3','2');
 $checksum=0;
 for($i=0;$i
 $checksum += substr($idcard_base,$i,1) * $factor[$i];
 }
 $mod=$checksum % 11;
 $verify_number=$verify_number_list[$mod];
 return $verify_number;
}
// Upgrade the 15-digit ID card to 18 digits
function idcard_15to18($idcard){
 if(strlen($idcard)!=15){
 return false;
 }else{
 / / If the ID card sequence code is 996 997 998 999, these are special codes for people over 100 years old
 if(array_search(substr($idcard,12,3),array('996','997','998' ,'999')) !== false){
 $idcard=substr($idcard,0,6).'18'.substr($idcard,6,9);
 }else{
 $idcard=substr( $idcard,0,6).'19'.substr($idcard,6,9);
 }
 }
 $idcard=$idcard.idcard_verify_number($idcard);
 return $idcard;
}
// 18 Validity check of ID card verification code
function idcard_checksum18($idcard){
 if(strlen($idcard)!=18){
 return false;
 }
 $idcard_base=substr($idcard,0,17);
 if(idcard_verify_number($idcard_base)!=strtoupper(substr($idcard,17,1))){
 return false;
 }else{
 return true;
 }
}

Call method :

validation_filter_id_card('ID number');