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PHP的json_encode分析

WBOY
WBOY원래의
2016-06-06 19:57:11862검색

json的优点就不说了, 有个习惯,我在输出json的时候,喜欢用 sprintf 拼成json格式, 前两天被朋友说不标准,必须要用json_encode生成的才是标准的json格式,我当然很郁闷啦, 用了这么多年了,刚知道 这样做不标准,既然说我不标准,那上面才是标准的json

json的优点就不说了,

有个习惯,我在输出json的时候,喜欢用 sprintf 拼成json格式,

前两天被朋友说不标准,必须要用json_encode生成的才是标准的json格式,我当然很郁闷啦,

用了这么多年了,刚知道 这样做不标准,既然说我不标准,那上面才是标准的json格式?

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{a : 'abc'}

{'a' : 'abc'}

{a : "abc"}

{"a" : "abc"}

那都知道,只有第四种才是标准的json格式。

我这么做

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$ret_json='{"%s":"%s"}';

echo json_encode($ret_json,"a","abc");

必然也符合标准。

既然如此,那我就要刨根问底,json_encode生成的json格式究竟有什么不同?
上代码

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static PHP_FUNCTION(json_encode)

{

        zval *parameter;

        smart_str buf = {0};

        long options = 0;

 

        if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "z|l", &parameter, &options) == FAILURE) {

                return;

        }  

 

        JSON_G(error_code) = PHP_JSON_ERROR_NONE;

 

        php_json_encode(&buf, parameter, options TSRMLS_CC);

 

        ZVAL_STRINGL(return_value, buf.c, buf.len, 1);

 

        smart_str_free(&buf);

}


JSON_G(error_code) = PHP_JSON_ERROR_NONE;
是定义的json错误,该错误可以通过json_last_error函数获取,你用过吗?反正我没用过。
php_json_encode是主要的操作

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PHP_JSON_API void php_json_encode(smart_str *buf, zval *val, int options TSRMLS_DC) /* {{{ */

{

        switch (Z_TYPE_P(val))

        {

                case IS_NULL:

                        smart_str_appendl(buf, "null", 4); //输出NULL

                        break;

 

                case IS_BOOL:

                        if (Z_BVAL_P(val)) {

                                smart_str_appendl(buf, "true", 4);//输出true

                        } else {

                                smart_str_appendl(buf, "false", 5);//输出false

                        }

                        break;

 

                case IS_LONG:

                        smart_str_append_long(buf, Z_LVAL_P(val));//输出长整形的值

                        break;

 

                case IS_DOUBLE:

                        {

                                char *d = NULL;

                                int len;

                                double dbl = Z_DVAL_P(val);

 

                                if (!zend_isinf(dbl) && !zend_isnan(dbl)) {//非无穷尽

                                        len = spprintf(&d, 0, "%.*k", (int) EG(precision), dbl);

                                        smart_str_appendl(buf, d, len);

                                        efree(d);

                                } else {

                                        php_error_docref(NULL TSRMLS_CC, E_WARNING, "double %.9g does not conform to the JSON spec, encoded as 0", dbl);

                                        smart_str_appendc(buf, '0');

                                }

                       }

                        break;

 

                case IS_STRING://字符串

                        json_escape_string(buf, Z_STRVAL_P(val), Z_STRLEN_P(val), options TSRMLS_CC);

                        break;

 

                case IS_ARRAY://数组和对象

                case IS_OBJECT:

                        json_encode_array(buf, &val, options TSRMLS_CC);

                        break;

 

                default:

                        php_error_docref(NULL TSRMLS_CC, E_WARNING, "type is unsupported, encoded as null");

                        smart_str_appendl(buf, "null", 4);

                        break;

        }

 

        return;

}

很明显,根据不同的类型,会有相应的case。
最复杂的是 字符串 、数组 、对象这三种类型,数组和对象是同一种操作。
先看看字符串吧,很长,注释直接写在代码里。

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//options应该是5.3版本之后才支持的,由以下常量组成的二进制掩码: JSON_HEX_QUOT, JSON_HEX_TAG, JSON_HEX_AMP, JSON_HEX_APOS, JSON_NUMERIC_CHECK, JSON_PRETTY_PRINT, JSON_UNESCAPED_SLASHES, JSON_FORCE_OBJECT, JSON_UNESCAPED_UNICODE.虽然我没用过。。。

static void json_escape_string(smart_str *buf, char *s, int len, int options TSRMLS_DC) /* {{{ */

{

        int pos = 0;

        unsigned short us;

        unsigned short *utf16;

 

        if (len == 0) {//如果长度为0,则直接返回 双引号 ""

                smart_str_appendl(buf, "\"\"", 2);

                return;

        }

 

        if (options & PHP_JSON_NUMERIC_CHECK) {//检测是否为0-9的数字,如果是数字,那么就会直接把数据作为long或double类型返回。

                double d;

                int type;

                long p;

 

                if ((type = is_numeric_string(s, len, &p, &d, 0)) != 0) {

                        if (type == IS_LONG) {

                                smart_str_append_long(buf, p);

                        } else if (type == IS_DOUBLE) {

                                if (!zend_isinf(d) && !zend_isnan(d)) {

                                        char *tmp;

                                        int l = spprintf(&tmp, 0, "%.*k", (int) EG(precision), d);

                                        smart_str_appendl(buf, tmp, l);

                                        efree(tmp);

                                } else {

                                        php_error_docref(NULL TSRMLS_CC, E_WARNING, "double %.9g does not conform to the JSON spec, encoded as 0", d);

                                        smart_str_appendc(buf, '0');

                                }

                        }

                        return;

                }

 

        }

 

        utf16 = (unsigned short *) safe_emalloc(len, sizeof(unsigned short), 0);

        len = utf8_to_utf16(utf16, s, len); //这里会对你输入的值一次处理转成对应的Dec码,比如1是49,a是97这样的,保存到utf16中。

        if (len <code>//如果len小于0 说明出错。如果用json_encode处理GBK的编码,就会在这里挂掉。

                if (utf16) {

                        efree(utf16);

                }

                if (len

                        JSON_G(error_code) = PHP_JSON_ERROR_UTF8;

                        if (!PG(display_errors)) {

                                php_error_docref(NULL TSRMLS_CC, E_WARNING, "Invalid UTF-8 sequence in argument");

                        }

                        smart_str_appendl(buf, "null", 4);

                } else {

                        smart_str_appendl(buf, "\"\"", 2);

                }

                return;

        }

 

        smart_str_appendc(buf, '"'); //输入 \"

 

//下面这一段代码就是将一些特殊字符转义如 双引号,反斜线等等

        while (pos

        {

                us = utf16[pos++];

 

                switch (us)

                {

                        case '"':

                                if (options & PHP_JSON_HEX_QUOT) {

                                        smart_str_appendl(buf, "\\u0022", 6);

                                } else {

                                        smart_str_appendl(buf, "\\\"", 2);

                                }

                                break;

 

                        case '\\':

                                smart_str_appendl(buf, "\\\\", 2);

                                break;

case '/':

                                smart_str_appendl(buf, "\\/", 2);

                                break;

 

                        case '\b':

                                smart_str_appendl(buf, "\\b", 2);

                                break;

 

                        case '\f':

                                smart_str_appendl(buf, "\\f", 2);

                                break;

 

                        case '\n':

                                smart_str_appendl(buf, "\\n", 2);

                                break;

 

                        case '\r':

                                smart_str_appendl(buf, "\\r", 2);

                                break;

 

                        case '\t':

                                smart_str_appendl(buf, "\\t", 2);

                                break;

 

                        case '<code>:

                                if (options & PHP_JSON_HEX_TAG) {

                                        smart_str_appendl(buf, "\\u003C", 6);

                                } else {

                                        smart_str_appendc(buf, '<code>);

                                }

                                break;

 

                        case '>':

                                if (options & PHP_JSON_HEX_TAG) {

                                        smart_str_appendl(buf, "\\u003E", 6);

                                } else {

                                        smart_str_appendc(buf, '>');

}

                                break;

 

                        case '&':

                                if (options & PHP_JSON_HEX_AMP) {

                                        smart_str_appendl(buf, "\\u0026", 6);

                                } else {

                                        smart_str_appendc(buf, '&');

                                }

                                break;

 

                        case '\'':

                                if (options & PHP_JSON_HEX_APOS) {

                                        smart_str_appendl(buf, "\\u0027", 6);

                                } else {

                                        smart_str_appendc(buf, '\'');

                                }

                                break;

 

                        default: //一直到这里,没有特殊字符就会把值append到buf中

                                if (us >= ' ' && (us & 127) == us) {

                                        smart_str_appendc(buf, (unsigned char) us);

                                } else {

                                        smart_str_appendl(buf, "\\u", 2);

                                        us = REVERSE16(us);

 

                                        smart_str_appendc(buf, digits[us & ((1

                                        us >>= 4;

                                        smart_str_appendc(buf, digits[us & ((1

                                        us >>= 4;

                                        smart_str_appendc(buf, digits[us & ((1

                                        us >>= 4;

                                        smart_str_appendc(buf, digits[us & ((1

                                }

                                break;

                }

        }

        smart_str_appendc(buf, '"'); //结束 双引号。

        efree(utf16);

}

再来看看数组和对象,也很简单,

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static void json_encode_array(smart_str *buf, zval **val, int options TSRMLS_DC) /* {{{ */

{

        int i, r;

        HashTable *myht;

 

        if (Z_TYPE_PP(val) == IS_ARRAY) {

                myht = HASH_OF(*val);

                r = (options & PHP_JSON_FORCE_OBJECT) ? PHP_JSON_OUTPUT_OBJECT : json_determine_array_type(val TSRMLS_CC);

        } else {

                myht = Z_OBJPROP_PP(val);

                r = PHP_JSON_OUTPUT_OBJECT;

        }  

 

        if (myht && myht->nApplyCount > 1) {

                php_error_docref(NULL TSRMLS_CC, E_WARNING, "recursion detected");

                smart_str_appendl(buf, "null", 4);

                return;

        }

        if (r == PHP_JSON_OUTPUT_ARRAY) {

                smart_str_appendc(buf, '[');

        } else {

                smart_str_appendc(buf, '{');

        }  

 

        i = myht ? zend_hash_num_elements(myht) : 0;

 

        if (i > 0)

        {

                char *key;

                zval **data;

                ulong index;

                uint key_len;

                HashPosition pos;

                HashTable *tmp_ht;

                int need_comma = 0;

 

                zend_hash_internal_pointer_reset_ex(myht, &pos);

//便利哈希表

                for (;; zend_hash_move_forward_ex(myht, &pos)) {

                        i = zend_hash_get_current_key_ex(myht, &key, &key_len, &index, 0, &pos);

                        if (i == HASH_KEY_NON_EXISTANT)

                                break;

 

                        if (zend_hash_get_current_data_ex(myht, (void **) &data, &pos) == SUCCESS) {

                                tmp_ht = HASH_OF(*data);

                                if (tmp_ht) {

                                        tmp_ht->nApplyCount++;

                                }

 

                                if (r == PHP_JSON_OUTPUT_ARRAY) {

                                        if (need_comma) {

                                                smart_str_appendc(buf, ',');

                                        } else {

                                                need_comma = 1;

                                        }

//将值append到 buf中

                                        php_json_encode(buf, *data, options TSRMLS_CC);

                                } else if (r == PHP_JSON_OUTPUT_OBJECT) {

                                        if (i == HASH_KEY_IS_STRING) {

                                                if (key[0] == '\0' && Z_TYPE_PP(val) == IS_OBJECT) {

                                                        /* Skip protected and private members. */

                                                        if (tmp_ht) {

                                                                tmp_ht->nApplyCount--;

                                                        }

                                                        continue;

                                                }

 

                                                if (need_comma) {

                                                        smart_str_appendc(buf, ',');

                                                } else {

                                                        need_comma = 1;

                                                }

 

                                                json_escape_string(buf, key, key_len - 1, options & ~PHP_JSON_NUMERIC_CHECK TSRMLS_CC);

                                                smart_str_appendc(buf, ':');

 

                                                php_json_encode(buf, *data, options TSRMLS_CC);

                                        } else {

                                                if (need_comma) {

                                                        smart_str_appendc(buf, ',');

                                                } else {

                                                        need_comma = 1;

                                                }

 

                                                smart_str_appendc(buf, '"');

                                 &n

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