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。
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