(转)addslashes与mysql_real_escape_string的区别

我们为了更深层次的探究这两个函数的不同..还是去看一看PHP的源码吧..





这是PHP的addslashes函数..





PHP_FUNCTION(addslashes)

{

zval **str;



if (ZEND_NUM_ARGS() !&＃61; 1 || zend_get_parameters_ex(1, &str) &＃61;&＃61; FAILURE) {

WRONG_PARAM_COUNT;

}

convert_to_string_ex(str);



if (Z_STRLEN_PP(str) &＃61;&＃61; 0) {

RETURN_EMPTY_STRING();

}



RETURN_STRING(php_addslashes(Z_STRVAL_PP(str),

Z_STRLEN_PP(str),

&Z_STRLEN_P(return_value), 0

TSRMLS_CC), 0);

}



很显然.它调用了php_addslashes.我们继续看这个函数





PHPAPI char *php_addslashes(char *str, int length, int *new_length, int should_free TSRMLS_DC)

{

return php_addslashes_ex(str, length, new_length, should_free, 0 TSRMLS_CC);

}



结果又是是在调用php_addslashes_ex 我们就像在剥洋葱一样..一步一步的接近真理..





PHPAPI char *php_addslashes_ex(char *str, int length, int *new_length, int should_free, int ignore_sybase TSRMLS_DC)

{

/* maximum string length, worst case situation */

char *new_str;

char *source, *target;

char *end;

int local_new_length;



if (!new_length) {

new_length &＃61; &local_new_length;

}

if (!str) {

*new_length &＃61; 0;

return str;

}

new_str &＃61; (char *) safe_emalloc(2, (length ? length : (length &＃61; strlen(str))), 1);

source &＃61; str;

end &＃61; source &＃43; length;

target &＃61; new_str;



if (!ignore_sybase && PG(magic_quotes_sybase)) {

while (source
switch (*source) {

case &＃39;\0&＃39;:

*target&＃43;&＃43; &＃61; &＃39;\\&＃39;;

*target&＃43;&＃43; &＃61; &＃39;0&＃39;;

break;

case &＃39;\&＃39;&＃39;:

*target&＃43;&＃43; &＃61; &＃39;\&＃39;&＃39;;

*target&＃43;&＃43; &＃61; &＃39;\&＃39;&＃39;;

break;

default:

*target&＃43;&＃43; &＃61; *source;

break;

}

source&＃43;&＃43;;

}

} else {

while (source
switch (*source) {

case &＃39;\0&＃39;:

*target&＃43;&＃43; &＃61; &＃39;\\&＃39;;

*target&＃43;&＃43; &＃61; &＃39;0&＃39;;

break;

case &＃39;\&＃39;&＃39;:

case &＃39;\"&＃39;:

case &＃39;\\&＃39;:

*target&＃43;&＃43; &＃61; &＃39;\\&＃39;;

/* break is missing *intentionally* */

default:

*target&＃43;&＃43; &＃61; *source;

break;

}



source&＃43;&＃43;;

}

}



*target &＃61; 0;

*new_length &＃61; target - new_str;

if (should_free) {

STR_FREE(str);

}

new_str &＃61; (char *) erealloc(new_str, *new_length &＃43; 1);

return new_str;

}



上面的函数已经非常清楚的描述出都要转义哪些字符了..现在我们去看一看mysql_real_escape_string



这个不在string.c里了..是在mysql扩展中.





PHP_FUNCTION(mysql_real_escape_string)

{

zval *mysql_link &＃61; NULL;

char *str;

char *new_str;

int id &＃61; -1, str_len, new_str_len;

php_mysql_conn *mysql;





if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|r", &str, &str_len, &mysql_link) &＃61;&＃61; FAILURE) {

return;

}



if (ZEND_NUM_ARGS() &＃61;&＃61; 1) {

id &＃61; php_mysql_get_default_link(INTERNAL_FUNCTION_PARAM_PASSTHRU);

CHECK_LINK(id);

}



ZEND_FETCH_RESOURCE2(mysql, php_mysql_conn *, &mysql_link, id, "MySQL-Link", le_link, le_plink);



new_str &＃61; safe_emalloc(str_len, 2, 1);

new_str_len &＃61; mysql_real_escape_string(&mysql->conn, new_str, str, str_len);

new_str &＃61; erealloc(new_str, new_str_len &＃43; 1);



RETURN_STRINGL(new_str, new_str_len, 0);

}



这个函数并没有像上面的那样剥洋葱..



而是直接调用了MySql的C的API.mysql_real_escape_string()..



需要注意的是.这个函数在调用mysql_real_escape_string这个API之前.先是判断了是否连接上了数据库



CHECK_LINK(id); //就是这句



所以这就意味着mysql_real_escape_string必须是连接数据库之后才能使用.为了证实这一点.



我们来简单的实验下.






echo mysql_real_escape_string("fdsafda&＃39;fdsa");



结果



Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: Access denied for user ‘ODBC’&＃64;&＃39;localhost’ (using password: NO) in PHPDocument1 on line 2



Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: A link to the server could not be established in PHPDocument1 on line 2



果然报错了..显示没有链接上数据库..



好了..总结就先告一段落..



我们终于明白为什么那么多开源的程序比如Discuz用addslashes而不用mysql_real_escape_string了.



所以呢.以后也就用addslashes好了..暂时可以忘记掉mysql_real_escape_string了:)