create foreign key in sql using php code example

Example 1: create foreign key phpmyadmin

ALTER TABLE table_name
ADD CONSTRAINT fk_foreign_key_name
FOREIGN KEY (foreign_key_name)
REFERENCES target_table(target_key_name);

Example 2: foreign key in php

CREATE TABLE Orders (
    OrderID int NOT NULL,
    OrderNumber int NOT NULL,
    PersonID int,
    PRIMARY KEY (OrderID),
    CONSTRAINT FK_PersonOrder FOREIGN KEY (PersonID)
    REFERENCES Persons(PersonID)
);