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PHP json_encode usage analysis instructions_PHP tutorial

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Release: 2016-07-13 17:07:31
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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)。

www.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...
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