Following are different 3 ways to prevent from SQL Injection.
1. Using PHP inbuilt Functions.
$name = mysql_real_escape_string($_POST["name"]); mysql_query("INSERT INTO users VALUES($name)");
2. Use MySqli instead of MySQL. MySqli is far better than MySql because is object oriented MySql.
$stmt = $dbConnection->prepare('INSERT INTO users VALUES(?)'); $name=$_POST["name"]; $stmt->bind_param('s', $name); $stmt->execute();
3. Using PDO
$stmt = $conn->prepare("INSERT INTO users VALUES(:name)"); $stmt->bindValue(':name', $_POST["name"]); $stmt->execute();