本文实例讲述了PHP+mysql防止SQL注入的方法。分享给大家供大家参考，具体如下：

SQL注入

例：脚本逻辑

$sql = "SELECT * FROM user WHERE userid = $_GET[userid] ";

案例1：

SELECT * FROM t WHERE a LIKE '%xxx%' OR (IF(NOW=SYSDATE(), SLEEP(5), 1)) OR b LIKE '1=1 ';

案例2：

SELECT * FROM t WHERE a > 0 AND b IN(497 AND (SELECT * FROM (SELECT(SLEEP(20)))a) );

案例3：

SELECT * FROM t WHERE a=1 and b in (1234 ,(SELECT (CASE WHEN (5=5) THEN SLEEP(5) ELSE 5*(SELECT 5 FROM INFORMATION_SCHEMA.CHARACTER_SETS) END)) );

监控以下方法

SLEEP() — 一般的SQL盲注都会伴随SLEEP()函数出现，而且一般至少SLEEP 5秒以上

MID()

CHAR()

ORD()

SYSDATE()

SUBSTRING()

DATABASES()

SCHEMA()

USER()

VERSION()

CURRENT_USER()

LOAD_FILE()

OUTFILE/DUMPFILE

INFORMATION_SCHEMA

TABLE_NAME

fwrite()/fopen()/file_get_contents() — 这几个是PHP文件操作函数

应对方法：

1.mysql_escape_string() 转义特殊字符((PHP 4 >= 4.3.0, PHP 5))(mysql_real_escape_string必须先链接上数据库，否则会报错)

下列字符受影响：

\x00 //对应于ascii字符的NULL

\n  //换行符且回到下一行的最前端

\r //换行符

\ //转义符

'

"

\x1a  //16进制数

如果成功，则该函数返回被转义的字符串。如果失败，则返回 false。

2.addslashes(): 函数返回在预定义字符之前添加反斜杠的字符串 (stripslashes()实现字符串还原)

预定义的字符有：

单引号(')

双引号(")

反斜杠(\)

NULL

3.prepared  statements(预处理机制)

$mysqli = new mysqli("example.com", "user", "password", "database");

if ($mysqli->connect_errno) {

echo "Failed to connect to MySQL: (" . $mysqli->connect_errno . ") " . $mysqli->connect_error;

}

/* Non-prepared statement */

if (!$mysqli->query("DROP TABLE IF EXISTS test") || !$mysqli->query("CREATE TABLE test(id INT)")) {

echo "Table creation failed: (" . $mysqli->errno . ") " . $mysqli->error;

}

/* Prepared statement, stage 1: prepare */

if (!($stmt = $mysqli->prepare("INSERT INTO test(id) VALUES (?)"))) {

echo "Prepare failed: (" . $mysqli->errno . ") " . $mysqli->error;

}

/* Prepared statement, stage 2: bind and execute */

$id = 1;

if (!$stmt->bind_param("i", $id)) {

echo "Binding parameters failed: (" . $stmt->errno . ") " . $stmt->error;

}

if (!$stmt->execute()) {

echo "Execute failed: (" . $stmt->errno . ") " . $stmt->error;

}

?>

希望本文所述对大家PHP程序设计有所帮助。