PHP的json_encode使用分析说明_PHP教程

本文章来给大家介绍json_encode使用分析，兴趣了解php源码的朋友可尝试参考哦。

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？

代码如下	复制代码
{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

代码如下	复制代码
$ret_json='{"%s":"%s"}'; echo json_encode($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

代码如下

复制代码

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", ¶meter, &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

代码如下

复制代码

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。

代码如下

复制代码

/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                 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 '                                 if (options & PHP_JSON_HEX_TAG) {                                         smart_str_appendl(buf, "\u003C", 6);                                 } else {                                         smart_str_appendc(buf, '                                 }                                 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，

代码如下

复制代码

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;         } //开始标签         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] == '' && 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, '"');                                                 smart_str_append_long(buf, (long) index);                                                 smart_str_appendc(buf, '"');                                                 smart_str_appendc(buf, ':');                                                   php_json_encode(buf, *data, options TSRMLS_CC);                                         }                                 }                                   if (tmp_ht) {                                         tmp_ht->nApplyCount--;                                 }                         }                 }         } //结束标签         if (r == PHP_JSON_OUTPUT_ARRAY) {                 smart_str_appendc(buf, ']');         } else {                 smart_str_appendc(buf, '}');         } }

通过简单分析，证明了一个问题，跟我上面用sprintf的方法其实是一样的，都是拼接字符串，

而且 为了性能，更应该鼓励用sprintf来拼接json格式，

因为 json_encode会进行很多 循环操作，而且所消耗的性能是线性的 O(n^2)。

http://www.bkjia.com/PHPjc/629905.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/629905.htmlTechArticle本文章来给大家介绍json_encode使用分析，兴趣了解php源码的朋友可尝试参考哦。 json的优点就不说了， 有个习惯，我在输出json的时候，喜欢...