Check and Retrieve those results where a cell(row) contains atleast one value from many values in a column
If I were doing this in SQL Server*, I would use:

USE tempdb;

CREATE TABLE Posts
(
    PostID INT NOT NULL IDENTITY(1,1)
    , PostName VARCHAR(255)
    /*  whatever other fields relate to POSTS */
    , CONSTRAINT PK_Posts PRIMARY KEY CLUSTERED (PostID) 
);
CREATE TABLE People
(
    PeopleID INT NOT NULL IDENTITY(1,1)
    , PersonName VARCHAR(255)
    /* whatever other fields relate to PEOPLE */
    , CONSTRAINT PK_People PRIMARY KEY CLUSTERED (PeopleID) 
);
CREATE TABLE PostsPeopleXRef
(
    PostID INT NOT NULL 
    , PeopleID INT NOT NULL 
    , CONSTRAINT FK_PostsPeopleXRef_PostID 
        FOREIGN KEY (PostID) REFERENCES Posts(PostID)
    , CONSTRAINT FK_PostsPeopleXRef_PeopleID 
        FOREIGN KEY (PeopleID) REFERENCES People(PeopleID)
);

INSERT INTO Posts (PostName) VALUES ('Post Test 1');
INSERT INTO People (PersonName) VALUES ('Jack');
INSERT INTO People (PersonName) VALUES ('Jill');
INSERT INTO People (PersonName) VALUES ('John');
INSERT INTO PostsPeopleXRef (PostID, PeopleID) VALUES (1, 1);
INSERT INTO PostsPeopleXRef (PostID, PeopleID) VALUES (1, 2);
INSERT INTO PostsPeopleXRef (PostID, PeopleID) VALUES (1, 3);

SELECT *
FROM dbo.Posts;

SELECT *
FROM dbo.People;

SELECT P.PostName, E.PersonName
FROM dbo.PostsPeopleXRef X
    INNER JOIN dbo.Posts P ON X.PostID = P.PostID
    INNER JOIN dbo.People E ON X.PeopleID = E.PeopleID
ORDER BY P.PostName
    , E.PersonName;


This results in the following output:



*
: for MySQL, you'll need some changes, like replacing IDENTITY(1,1) with AUTO_INCREMENT, removing the CLUSTERED keyword, adding the ENGINE = InnoDB at the CREATE TABLE statements, etc.