Error in SQL Syntax - ' '', '', now())'

Question

I am trying to insert a row into database and im getting the following error.

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' '', '', now())' at line 1.

And if I use single quote outside $gradeid it will get converted to string and since my database column is integer and it is also a foreign key, even this gets failed with the following error

Cannot add or update a child row: a foreign key constraint fails (`mydb`.`mytable1`, CONSTRAINT `activitygoalmaster_ibfk_1` FOREIGN KEY (`intGradeID`) REFERENCES `mytable2` (`intGradeID`))

Im not getting whats the error? May be some simple mistake but Im not getting it. Please help. My code in php is

  $title = $_POST['Title'];
  $gradeid = $_POST['GradeID'];
  $masterimgpath = $_POST['MasterImgPath'];
  $description = $_POST['Description'];

  $sql = "INSERT INTO activitygoalmaster(vchTitle, intGradeID, vchMasterImgPath, vchDescription, dtCreatedAt)VALUES('$title', $gradeid, '$masterimgpath', '$description', now())";
  $result = mysql_query($sql);

Answer 1

Looks like gradeid is empty. Try to verify it.

Do not use mysql-* functions, because this is deprecated. Use mysqli_* or pdo with prepared statement.

Answer 2

Please check table structure and his value.

print your $sql before execute it. so you can find error easily.

Answer 3

I have a question: intGradeID column is int() right? Is it a varchar() ? If it is a varchar() then it really needs single quotes in the insert query.

To solve the error with a foreign key constraint fails , please insert to mytable2 the grade id first before inserting it to mytable1 . It shows this error because it is required by a foreign key on mytable1 .