一応、次のようにすればできます。
php
1$family_name = $_POST['family_name'];
2$first_name = $_POST['first_name'];
3$sex = $_POST['sex'];
4if(empty($sex)){
5 $sex = 'NULL';
6}
7$grading = $_POST['grading'];
8if(empty($grading)){
9 $grading = 'NULL';
10}
11$email = $_POST['email'];
12
13$sql = "insert into account(";
14$sql .= "family_name,";
15$sql .= "first_name,";
16$sql .= "sex,";
17$sql .= "grading,";
18$sql .= "email,";
19
20
21$sql .="values(\""
22 .$family_name."\",\""
23 .$first_name."\","
24 .$sex.","
25 .$grading.",\""
26 .$email."\")";
ですが、POSTされてきたものをそのままSQLに利用するのは大変危険です。
プリペアドステートメントの利用やエスケープする必要性があります。
指摘があったので修正
php
1$family_name = $_POST['family_name'];
2$first_name = $_POST['first_name'];
3$sex = $_POST['sex'];
4if(!isset($sex)){
5 $sex = 'NULL';
6}
7$grading = $_POST['grading'];
8if(!isset($grading)){
9 $grading = 'NULL';
10}
11$email = $_POST['email'];
12
13$sql = "insert into account(";
14$sql .= "family_name,";
15$sql .= "first_name,";
16$sql .= "sex,";
17$sql .= "grading,";
18$sql .= "email,";
19
20
21$sql .="values(\""
22 .$family_name."\",\""
23 .$first_name."\","
24 .$sex.","
25 .$grading.",\""
26 .$email."\")";
もう一度修正 ついでにSQLを作成する部分にも間違いがあったので修正
php
1$family_name = $_POST['family_name'];
2$first_name = $_POST['first_name'];
3$sex = $_POST['sex'];
4if(is_null($sex) || $sex === ''){
5 $sex = 'NULL';
6}
7$grading = $_POST['grading'];
8if(is_null($grading) || $grading === ''){
9 $grading = 'NULL';
10}
11$email = $_POST['email'];
12
13$sql = "insert into account(";
14$sql .= "family_name,";
15$sql .= "first_name,";
16$sql .= "sex,";
17$sql .= "grading,";
18$sql .= "email) ";
19
20
21$sql .="values(\""
22 .$family_name."\",\""
23 .$first_name."\","
24 .$sex.","
25 .$grading.",\""
26 .$email."\")";
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