The best solution to prevent SQL injection in php_PHP tutorial

If the user enters a query that is inserted directly into a SQL statement, the application will be vulnerable to SQL injection, such as the following example:

Copy codeThe code is as follows:

$unsafe_variable = $_POST['user_input'];
mysql_query("INSERT INTO table (column) VALUES ('" . $unsafe_variable . "')") ;

This is because the user can enter something like VALUE"); DROP TABLE table; - , making the query become:

Copy codeThe code is as follows:

INSERT INTO table (column) VALUES('VALUE'); DROP TABLE table;'

How should we prevent this What’s the situation? Let’s take a look at Theo’s answer

Use prepared statements and parameterized queries. SQL statements with any parameters will be sent to the database server and parsed! It is impossible for an attacker to maliciously inject SQL!

There are basically two options for achieving this:

1. Use PDO (PHP Data Objects)

Copy the code The code is as follows:

$stmt = $pdo->prepare('SELECT * FROM employees WHERE name = :name');

$stmt->execute(array(':name' => $name));

foreach ($stmt as $row) {
// do something with $row
}

2. Use mysqli

Copy code The code is as follows:

$stmt = $dbConnection->prepare('SELECT * FROM employees WHERE name = ?' );
$stmt->bind_param('s', $name);

$stmt->execute();

$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
// do something with $row
}

PDO (PHP Data Object)

Note that when using PDO to access the MySQL database, the real prepared statements are not used by default! To resolve this issue, you must disable emulation of prepared statements. An example of using PDO to create a connection is as follows:

Copy the code The code is as follows:

$dbConnection = new PDO('mysql:dbname =dbtest;host=127.0.0.1;charset=utf8', 'user', 'pass');
$dbConnection->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$dbConnection->setAttribute (PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

The error mode ERRMODE is not strictly required in the above example, but it is recommended to add it. This method does not stop the script when a fatal error occurs. And give the developer a chance to catch any errors (when PDOException is thrown). The

setAttribute() line is mandatory. It tells PDO to disable simulated prepared statements and use real prepared statements. This ensures that statements and values ​​are not parsed by PHP before being sent to the MySQL database server (an attacker has no opportunity to inject malicious SQL).

Of course you can set the character set parameter in the constructor options, especially note that 'old' PHP versions (5.3.6) will ignore the character set parameter in the DSN.

Explanation

What happens when the SQL prepared statement you pass is parsed and compiled by the database server? Tell the database engine what you want to filter by specifying characters (like a? or like: name in the above example). Then call execute to execute the prepared statement combined with the parameter value you specified.

The most important thing here is that the parameter value is combined with a precompiled statement, not with a SQL string. The working principle of SQL injection is to create a SQL script including a malicious string by deception and send it to the database. Therefore, by sending actual separate sql parameters, you will reduce the risk. When using prepared statements, any parameters you send, will only be treated as strings (although the database engine may do some parameter optimization, of course eventually may be a number). In the above example, if the variable $name contains 'sarah';DELETE * FROM employees, the result will only be a search string "'sarah';DELETE * FROM employees", you will not get An empty table.

Another benefit of using prepared statements is that if you execute the same statement multiple times in the same session, this will only be parsed and compiled once, giving you some speed gains.
Oh, since you asked how to do the insert, here is an example (using PDO):

Copy the code The code is as follows:

$preparedStatement = $db->prepare('INSERT INTO table (column) VALUES (:column)');
$preparedStatement->execute(array(':column' => $unsafeValue) );

http://www.bkjia.com/PHPjc/326796.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/326796.htmlTechArticleIf the user enters a query directly inserted into a SQL statement, the application will be vulnerable to SQL injection. For example, the following example: Copy the code as follows: $unsafe_variable =...