Just a note. When INSERTing a CLOB, if a VALUES clause is used, Oracle notes: You cannot initialize an internal LOB attribute in an object with a value other than empty or null. That is, you cannot use a literal.
That's why all the examples here INSERT an EMPTY_CLOB(), and use RETURNING to grab the pointer.
However, a CLOB can also be INSERTed via a SELECT statement, and that won't require any descriptors.
Example:
$Clob = Str_Replace("'", "''", $Clob);
OCIParse($DB, "INSERT INTO My_Table (My_Clob) SELECT '$Clob' FROM Dual");
This, of course, allows the use of a WHERE clause as well.