Large data import using PHP and mysql to multiple tables with foreign keys

You can import large files around millions of records in one shot from below method, please use mysql Load DATA

for ex-

LOAD DATA LOCAL INFILE  
'/PATH_TO_YOUR_CSV/YOUR_CSV.csv'
INTO TABLE MY_TABLE
FIELDS TERMINATED BY ',' 
ENCLOSED BY '"'
LINES TERMINATED BY '\n';

Please remember your table structure and your csv file structure (no of columns) should be same

-- import the csvfile to this temp table , the column just like your csv header
create table IF NOT EXISTS my_db.csv_file (

    id int auto_increment primary key,
    vendor_name varchar(200),
    product_name varchar(200),
    product_price double
    
);

-- table one
create table if not exists my_db.product(
    id int auto_increment primary key,
    vendor_id int, -- foreign
    name varchar(200),
    price double
)

-- table two
create table if not exists my_db.vendor(

    id int auto_increment primary key,
    name varchar(200)
)

-- import csv data ,you can use LOAD command 
insert into my_db.csv_file(vendor_name,product_name,product_price)values
('A','book',1.00),
('B','computer',2.00),
('C','phone',3.00);


-- step 1:

insert into my_db.vendor(name)
(select vendor_name from my_db.csv_file group by vendor_name);

-- step 2:
insert into my_db.product(vendor_id , name , price)
(select vendor.id,temp.product_name,temp.product_price from my_db.csv_file as temp left join my_db.vendor as vendor on vendor.name = temp.vendor_name);