php内置函数分析之array_change_key_case()

 PHP_FUNCTION(array_change_key_case)
 {
     zval *array, *entry;
     zend_string *string_key;
     zend_string *new_key;
     zend_ulong num_key;
     zend_long change_to_upper=;

     if (zend_parse_parameters(ZEND_NUM_ARGS(), "a|l", &array, &change_to_upper) == FAILURE) {
         return;
     }

     array_init_size(return_value, zend_hash_num_elements(Z_ARRVAL_P(array)));

     ZEND_HASH_FOREACH_KEY_VAL(Z_ARRVAL_P(array), num_key, string_key, entry) {
         if (!string_key) { // 数组键值为数字索引，将数组元素更新到return_value
             entry = zend_hash_index_update(Z_ARRVAL_P(return_value), num_key, entry);
         } else { // 数组键值为字符串
             // 字符串键值大小写转换
             if (change_to_upper) {
                 new_key = php_string_toupper(string_key);
             } else {
                 new_key = php_string_tolower(string_key);
             }
             // 将数组元素更新到return_value
             entry = zend_hash_update(Z_ARRVAL_P(return_value), new_key, entry);
             // 释放zend_string, 如果引用数位0，则释放内存。
             zend_string_release(new_key);
         }
         // 增加引用
         zval_add_ref(entry);
     } ZEND_HASH_FOREACH_END();
 }