PHP json_encode usage analysis instructions_PHP tutorial

This article will introduce you to the usage analysis of json_encode. Friends who are interested in understanding the php source code can try to refer to it.

I won’t talk about the advantages of json,

I have a habit, when I output json, I like to use sprintf to spell it into json format,

Two days ago, I was told by a friend that it was not standard and that json_encode must be used to generate the standard json format. Of course I was very depressed,

After using it for so many years, I just realized that this is not standard. Since I say it is not standard, then is the above the standard json format?

The code is as follows

Copy code

代码如下	复制代码
{a : 'abc'} {'a' : 'abc'} {a : "abc"} {"a" : "abc"}

{a : 'abc'} {'a' : 'abc'} {a : "abc"} {"a" : "abc"}

Everyone knows that only the fourth type is the standard json format.

I do this

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

The code is as follows	Copy code
$ret_json='{"%s":"%s"}'; echo json_encode($ret_json,"a","abc");

It must also meet the standards.

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); }

In this case, I have to ask more deeply, what is the difference between the json format generated by json_encode? Up code

The code is as follows

Copy code

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;
It is a defined json error. This error can be obtained through the json_last_error function. Have you used it? I haven't used it anyway.
php_json_encode is the main operation

The code is as follows

Copy code

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); // Output null                           break; case IS_BOOL: If (Z_BVAL_P(val)) { Smart_Str_appendl (buf, "true", 4); // Output true                              } else {                                                                                                                                                                                                                                                       out out out out out out out of false                                                                                                           }                           break; case IS_LONG: Smart_Str_append_long (buf, z_lval_p (val)); // Output the value of long plastic surgery                           break; case IS_DOUBLE:                                                                                                                                                                                                                                                                                                                                                               char *d = NULL; int len;                                                                                                                                                                                                                                      double dbl = Z_DVAL_P(val); If (!zend_isinf(dbl) && !zend_isnan(dbl)) {//Not infinite                                                                                                                                                                                                                                                       len = spprintf(&d, 0, "%.*k", (int) EG(precision), dbl);                                                                                                                                                                                                                                                     through 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; }

Obviously, there will be corresponding cases according to different types.
The most complex types are string, array, and object. Arrays and objects are the same operation.
Let’s take a look at the string first. It’s very long and the comments are written directly in the code.

The code is as follows

Copy code

/options should be supported only after version 5.3, and are binary masks composed of the following constants: 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. Although I haven't used it. . . 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) {//If the length is 0, return double quotes directly ""                       smart_str_appendl(buf, """", 2);                    return; } If (options & PHP_JSON_NUMERIC_CHECK) {//Check whether it is a number from 0 to 9, if it is a number, the data will be returned directly as a long or double type.                        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)) {                                                                                                int l = spprintf(&tmp, 0, "%.*k", (int) EG(precision), d);                                                                                                                                                                                                                                 smart_str_appendl (buf, tmp, l); efree(tmp);                                                                                                                                                                                                                                                                                      Php_error_docref (null TSRMLS_CC, E_WARNINING, "Double %.9g Does Not Conform to the Json Spec, Encoded as 0", d);                                                                                                                                                                                                                                                      through smart_str_appendc(buf, '0');                                                                                                                            }                                                                                                                                                return;                 } } ​​​​ utf16 = (unsigned short *) safe_emalloc(len, sizeof(unsigned short), 0); ​​​​​ len = utf8_to_utf16(utf16, s, len); //The value you input will be processed once and converted into the corresponding Dec code, such as 1 is 49, a is 97, and saved in utf16. If (len <= 0) {//If len is less than 0, an error occurs. If you use json_encode to process GBK encoding, it will hang up here. If (utf16) {                                efree(utf16);                 } If (len < 0) { 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, '"'); //Input " //The following code is to escape some special characters such as double quotes, backslashes, etc.            while (pos < len)             {                     us = utf16[pos++]; switch (us)                                                   { case '"': If (options & PHP_JSON_HEX_QUOT) {                                                                                                                                                                                                                           to                                                                                                                                                                                                                                                                                                                             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) {                                                                                                                                                                                                                           to                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         smart_str_appendc(buf, ''');                                                                                                                            } break; default: //Up to here, if there are no special characters, the value will be appended to buf If (us >= ' ' && (us & 127) == us) {                                                                                                                                                                                                                                                                 smart_str_appendc(buf, (unsigned char) us);                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  because Smart_Str_appendc (buf, digits [us & ((1 & lt; & lt; 4) - 1)];                                                                                                                                                  through Smart_Str_appendc (buf, digits [us & ((1 & lt; & lt; 4) - 1)];                                                                                                                                                  through Smart_Str_appendc (buf, digits [us & ((1 & lt; & lt; 4) - 1)];                                                                                                                                                  through Smart_Str_appendc (buf, digits [us & ((1 & lt; & lt; 4) - 1)];                                                                                                                                                                                                                                                                        break;                 } }           smart_str_appendc(buf, '"'); //End double quotes.         efree(utf16); }

Let’s look at arrays and objects, they are also very simple,

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...