How to solve the phpsql injection principle

For more information about phpsql injection principles, such as a URL & nbsp; www.xx.com/news.php? Id = 3 & nbsp; This link is followed by an & nbsp; '& nbsp; symbol, and an error is reported; 1 = principles of php SQL injection
For example, a URL www.xx.com/news.php? If the link id = 3 is followed by a 'symbol, an error is reported, or if the two return values are different, and 1 = 1 and then and 1 = 2, an injection point can be determined,

For example, www.xx.com/news.php? Id = 3. Why does an error occur after the select * from news where id = '3' symbol is added to the address bar in my SQL statement, and 1 = 1 and 1 = 2. Why do we know there are injection points: More