Oracle SQL Trigger Error- OCI_SUCCESS_WITH_INFO: ORA-24344 - php

Question

I am using a trigger called "users_id_trigger" to auto increment the users.user_id column.
But in Object Browser its status is showing invalid!
I am working on a PHP project where i am getting this error while i run the query from a PHP script. here is the error message:
oci_execute(): OCI_SUCCESS_WITH_INFO: ORA-24344: success with compilation error
Here is my method to create the entire table and related SEQUENCE and TRIGGER to be able to have auto increment feature in the user_id column.
public function create_users_table()
{
// creating users table
oci_execute(oci_parse($this->conn, "CREATE TABLE users(
user_id NUMBER(10) NOT NULL,
user_name VARCHAR2(100) NOT NULL,
user_password VARCHAR(100) NOT NULL,
user_email VARCHAR(100) NOT NULL,
user_location VARCHAR(100) NOT NULL,
CONSTRAINT users_pk PRIMARY KEY (user_id)
)"));
// creating users sequence
oci_execute(oci_parse($this->conn, "CREATE SEQUENCE users_seq
MINVALUE 1
START WITH 1
INCREMENT BY 1
NOCACHE;
"));
// creating user sequence trigger
echo oci_execute(oci_parse($this->conn, "CREATE OR REPLACE TRIGGER users_id_trigger
BEFORE INSERT ON users
FOR EACH ROW
BEGIN
:new.user_id := users_seq.nextval;
END;
"));
}
What i am doing wrong? because the table and sequence is created successfully but not the trigger.
EDIT:
while inserting a new row i got this error:
insert into users values(1, 'hasan', '1234',
'hdg#live.com', 'Dhaka, Bangladesh')
* ERROR at line 1: ORA-04098: trigger 'FLIPLISTS.USERS_ID_TRIGGER' is invalid and failed re-validation
Oracle Version i am using: Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production (Windows 10)
Compilation Error: ORA-04082: NEW or OLD references not allowed in table level triggers

Answer 1

If oracle version that you are using is less than 11g then Modify your trigger as below
CREATE OR REPLACE TRIGGER users_id_trigger
BEFORE INSERT ON users
FOR EACH ROW
BEGIN
select users_seq.nextval into :new.user_id from dual ;
END;

Answer 2

The issue is that you have newlines on windows,so remove them.
echo oci_execute(oci_parse($this->conn, trim(preg_replace('/\s+/', ' ', "CREATE OR REPLACE TRIGGER users_id_trigger
BEFORE INSERT ON users
FOR EACH ROW
BEGIN
:new.user_id := users_seq.nextval;
END;
"));));