- 本文地址: https://www.laruence.com/2008/11/07/581.html
- 转载请注明出处
主要探讨了PHP的大变量的生成过程。另外如果你注意到， 当在表单中提交的input的name中如果有点号的时候， 在PHP中会自动把点号处理成下划线。并且你很想知道这是为什么，在什么时候发生的？ 呵呵，本文也就这个问题做了回答。
首先明确一个问题，PHP的变量名中是不能包含点号的。 但是为了处理表单中的点号命名，PHP就会自动把点号(.)转换成下划线(_)。
要知道PHP是怎么处理的，首先我们要了解，$_GET, $_POST, $_COOKIE等变量的构造过程。
在每个请求到来以后，apache处理到response阶段的时候， 会将控制权交给PHP模块， PHP模块会在处理请求之前首先间接调用 php_request_startup (具体调用序列是send_php -> apache_php_module_main -> php_request_startup, 关于这部门可以参看我前面的文章（ PHP Life Cycle) , 在php_request_startup中：
int php_request_startup(TSRMLS_D)
{
int retval = SUCCESS;
#if PHP_SIGCHILD
signal(SIGCHLD, sigchld_handler);
#endif
if (php_start_sapi() == FAILURE) {
return FAILURE;
}
php_output_activate(TSRMLS_C);
sapi_activate(TSRMLS_C);
php_hash_environment(TSRMLS_C);
zend_try {
PG(during_request_startup) = 1;
php_output_activate(TSRMLS_C);
if (PG(expose_php)) {
sapi_add_header(SAPI_PHP_VERSION_HEADER, sizeof(SAPI_PHP_VERSION_HEADER)-1, 1);
}
} zend_catch {
retval = FAILURE;
} zend_end_try();
return retval;
}
注意其中的php_hash_environment(TSRMLS_C) 函数调用 ， 这个函数就是在请求处理前， 初始化请求相关的变量的函数。
这个函数定义在： main/php_variables.c中 ， 有兴趣的可以看看：
int php_hash_environment(TSRMLS_D)
{
char *p;
unsigned char _gpc_flags[5] = {0, 0, 0, 0, 0};
zend_bool jit_initialization = (PG(auto_globals_jit) && !PG(register_globals) && !PG(register_long_arrays));
struct auto_global_record {
char *name;
uint name_len;
char *long_name;
uint long_name_len;
zend_bool jit_initialization;
} auto_global_records[] = {
{ "_POST", sizeof("_POST"), "HTTP_POST_VARS", sizeof("HTTP_POST_VARS"), 0 },
{ "_GET", sizeof("_GET"), "HTTP_GET_VARS", sizeof("HTTP_GET_VARS"), 0 },
{ "_COOKIE", sizeof("_COOKIE"), "HTTP_COOKIE_VARS", sizeof("HTTP_COOKIE_VARS"), 0 },
{ "_SERVER", sizeof("_SERVER"), "HTTP_SERVER_VARS", sizeof("HTTP_SERVER_VARS"), 1 },
{ "_ENV", sizeof("_ENV"), "HTTP_ENV_VARS", sizeof("HTTP_ENV_VARS"), 1 },
{ "_FILES", sizeof("_FILES"), "HTTP_POST_FILES", sizeof("HTTP_POST_FILES"), 0 },
};
size_t num_track_vars = sizeof(auto_global_records)/sizeof(struct auto_global_record);
size_t i;
/* jit_initialization = 0; */
for (i=0; i<num_track_vars; i++) {
PG(http_globals)[i] = NULL;
}
for (p=PG(variables_order); p && *p; p++) {
switch(*p) {
case 'p':
case 'P':
if (!_gpc_flags[0] && !SG(headers_sent) && SG(request_info).request_method && !strcasecmp(SG(request_info).request_method, "POST")) {
sapi_module.treat_data(PARSE_POST, NULL, NULL TSRMLS_CC); /* POST Data */
_gpc_flags[0] = 1;
if (PG(register_globals)) {
php_autoglobal_merge(&EG(symbol_table), Z_ARRVAL_P(PG(http_globals)[TRACK_VARS_POST]) TSRMLS_CC);
}
}
break;
....以下省略：
}}}
到了这里说个题外话， 就是在php.ini中， 可以使用variables_order来控制PHP是否生成某个大变量，已经大变量的生成顺序。
关于顺序，就是说， 如果打开了auto_register_globals的情况下， 如果先处理p，后处理g，那么$_GET['a'],就会覆盖$_POST['a'];
可以看到，离成功不远了，sapi_module.treat_data 也就是php_default_treat_data,
在php_default_treat_data中，对于变量，都调用php_register_variable_safe来注册变量， 而php_register_variable_safe最终会调用php_register_variable_ex:
PHPAPI void php_register_variable_ex(char *var, zval *val, zval *track_vars_array TSRMLS_DC)
{
char *p = NULL;
char *ip; /* index pointer */
char *index, *escaped_index = NULL;
int var_len, index_len;
zval *gpc_element, **gpc_element_p;
zend_bool is_array = 0;
HashTable *symtable1 = NULL;
assert(var != NULL);
if (track_vars_array) {
symtable1 = Z_ARRVAL_P(track_vars_array);
} else if (PG(register_globals)) {
symtable1 = EG(active_symbol_table);
}
if (!symtable1) {
/* Nothing to do */
zval_dtor(val);
return;
}
/*
* Prepare variable name
*/
/* ignore leading spaces in the variable name */
while (*var && *var==' ') {
var++;
}
/* ensure that we don't have spaces or dots in the variable name (not binary safe) */
//特别注意以下这段。。。。
for (p = var; *p; p++) {
if (*p == ' ' || *p == '.') {
*p='_';
} else if (*p == '[') {
is_array = 1;
ip = p;
*p = 0;
break;
}
....以下省略
呵呵，问题的原因找到了， 就是在php_register_variable的时候，会将(.)转换成（_).
最后,再介绍下$_REQUEST变量的生成, 其实很简单, 在php_hash_environment中的最后, 会调用 php_auto_globals_create_request("_REQUEST", sizeof("_REQUEST")-1 TSRMLS_CC)来注册_REQUEST大变量, 在php_auto_globals_create_request("_REQUEST", sizeof("_REQUEST")-1 TSRMLS_CC)中,只是简单的将$_GET, $_POST, $_COOKIE merge起来(G(http_globals)[TRACK_VARS_COOKIE]这部分,可以参看我较早前的) :
static zend_bool php_auto_globals_create_request(char *name, uint name_len TSRMLS_DC)
{
zval *form_variables;
unsigned char _gpc_flags[3] = {0, 0, 0};
char *p;
ALLOC_ZVAL(form_variables);
array_init(form_variables);
INIT_PZVAL(form_variables);
for (p = PG(variables_order); p && *p; p++) {
switch (*p) {
case 'g':
case 'G':
if (!_gpc_flags[0]) {
php_autoglobal_merge(Z_ARRVAL_P(form_variables), Z_ARRVAL_P(PG(http_globals)[TRACK_VARS_GET]) TSRMLS_CC);
_gpc_flags[0] = 1;
}
break; case 'p':
case 'P':
if (!_gpc_flags[1]) {
php_autoglobal_merge(Z_ARRVAL_P(form_variables), Z_ARRVAL_P(PG(http_globals)[TRACK_VARS_POST]) TSRMLS_CC);
_gpc_flags[1] = 1;
}
break;
case 'c':
case 'C': if (!_gpc_flags[2]) {
php_autoglobal_merge(Z_ARRVAL_P(form_variables), Z_ARRVAL_P(PG(http_globals)[TRACK_VARS_COOKIE]) TSRMLS_CC);
_gpc_flags[2] = 1;
}
break;
}
}
zend_hash_update(&EG(symbol_table), "_REQUEST", sizeof("_REQUEST"), &form_variables, sizeof(zval *), NULL);
return 0;
}
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Awesome! Its really amazing post, I have got much clear
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请问 TSRMLS_CC 是什么，起什么作用呢？
别的情况下无所谓，但是做签名验证的时候会导致bug，只能用php://input获取原始数据流
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辛苦辛苦，我这边也在进行这项任务，对比你的阅读过程，有些受益。谢谢
[…] 下午睡觉睡不着，起来接着看PHP的内核，想要了解一下PHP中的预定义变量实现过程。对比Laruence的《PHP的GET/POST等大变量生成过程》及TIPI的《第三节 预定义变量》，$_POST、$_GET等预定义变量初始化的过程应该是通过php_request_startup()函数调用php_hash_environment()来进行初始化的。然而找到main/php_variables.c中的php_hash_environment()函数却是如下： […]
[…] · 本文地址: http://www.laruence.com/2008/11/07/581.html · 转载请注明出处 […]
[…] 本文地址: http://www.laruence.com/2008/11/07/581.html […]
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[…] 那么, 我们今天就重点关注下, Query String是如何构建成_GET数组的(关于GET变量的生成, 请一并阅读我之前的文章: “PHP的GET/POST等大变量生成过程“): […]
[…] 那么, 我们今天就重点关注下, Query String是如何构建成_GET数组的(关于GET变量的生成, 请一并阅读我之前的文章: “PHP的GET/POST等大变量生成过程“): […]
[…] 那么, 我们今天就重点关注下, Query String是如何构建成_GET数组的(关于GET变量的生成, 请一并阅读我之前的文章: “PHP的GET/POST等大变量生成过程“): […]
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[…] 那么, 我们今天就重点关注下, Query String是如何构建成_GET数组的(关于GET变量的生成, 可以参看我之前的文章: “PHP的GET/POST等大变量生成过程“): […]
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呵呵，找到了，在php_globals.h里面定义的。
#ifdef ZTS
# define PG(v) TSRMG(core_globals_id, php_core_globals *, v)
extern PHPAPI int core_globals_id;
#else
# define PG(v) (core_globals.v)
extern ZEND_API struct _php_core_globals core_globals;
#endif
想问个问题，PG作什么用的。
宏的定义在哪，一直找不到
PG是为了兼容线程安全模式的一种对php_globals的访问包装， 定义在 main/php_globals.h(php 5.x)