$test=array();
for($run=0; $run<10000; $run++)
$test[]=rand(0,100);

$time=microtime(true);

$out = array_unique($test);

$time=microtime(true)-$time;
echo 'Array Unique: '.$time."\n";

$time=microtime(true);

$out=array_keys(array_flip($test));

$time=microtime(true)-$time;
echo 'Keys Flip: '.$time."\n";

$time=microtime(true);

$out=array_flip(array_flip($test));

$time=microtime(true)-$time;
echo 'Flip Flip: '.$time."\n";

/* {{{ proto array array_keys(array input [, mixed search_value[, bool strict]])
  Return just the keys from the input array, optionally only for the specified       search_value */
PHP_FUNCTION(array_keys)
{
  //变量定义
  zval *input,        /* Input array */
     *search_value = NULL,  /* Value to search for */
     **entry,        /* An entry in the input array */
      res,          /* Result of comparison */
     *new_val;        /* New value */
  int  add_key;        /* Flag to indicate whether a key should be added */
  char *string_key;      /* String key */
  uint  string_key_len;
  ulong num_key;        /* Numeric key */
  zend_bool strict = 0;    /* do strict comparison */
  HashPosition pos;
  int (*is_equal_func)(zval *, zval *, zval * TSRMLS_DC) = is_equal_function;

  //程序解析参数
  if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a|zb", &input, &search_value, &strict) == FAILURE) {
    return;
  }

  // 如果strict是true，则设置is_equal_func为is_identical_function，即全等比较
  if (strict) {
    is_equal_func = is_identical_function;
  }

  /* 根据search_vale初始化返回的数组大小 */
  if (search_value != NULL) {
    array_init(return_value);
  } else {
    array_init_size(return_value, zend_hash_num_elements(Z_ARRVAL_P(input)));
  }
  add_key = 1;

  /* 遍历输入的数组参数，然后添加键值到返回的数组 */
  zend_hash_internal_pointer_reset_ex(Z_ARRVAL_P(input), &pos);//重置指针
  //循环遍历数组
  while (zend_hash_get_current_data_ex(Z_ARRVAL_P(input), (void **)&entry, &pos) == SUCCESS) {
    // 如果search_value不为空
    if (search_value != NULL) {
      // 判断search_value与当前的值是否相同，并将比较结果保存到add_key变量
      is_equal_func(&res, search_value, *entry TSRMLS_CC);
      add_key = zval_is_true(&res);
    }

    if (add_key) {
      // 创建一个zval结构体
      MAKE_STD_ZVAL(new_val);

      // 根据键值是字符串还是整型数字将值插入到return_value中
      switch (zend_hash_get_current_key_ex(Z_ARRVAL_P(input), &string_key, &string_key_len, &num_key, 1, &pos)) {
        case HASH_KEY_IS_STRING:
          ZVAL_STRINGL(new_val, string_key, string_key_len - 1, 0);
          // 此函数负责将值插入到return_value中，如果键值已存在，则使用新值更新对应的值，否则直接插入
          zend_hash_next_index_insert(Z_ARRVAL_P(return_value), &new_val, sizeof(zval *), NULL);
          break;

        case HASH_KEY_IS_LONG:
          Z_TYPE_P(new_val) = IS_LONG;
          Z_LVAL_P(new_val) = num_key;
          zend_hash_next_index_insert(Z_ARRVAL_P(return_value), &new_val, sizeof(zval *), NULL);
          break;
      }
    }

    // 移动到下一个
    zend_hash_move_forward_ex(Z_ARRVAL_P(input), &pos);
  }
}
/* }}} */

/* {{{ proto array array_flip(array input)
  Return array with key <-> value flipped */
PHP_FUNCTION(array_flip)
{
  // 定义变量
  zval *array, **entry, *data;
  char *string_key;
  uint str_key_len;
  ulong num_key;
  HashPosition pos;

  // 解析数组参数
  if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a", &array) == FAILURE) {
    return;
  }

  // 初始化返回数组
  array_init_size(return_value, zend_hash_num_elements(Z_ARRVAL_P(array)));

  // 重置指针
  zend_hash_internal_pointer_reset_ex(Z_ARRVAL_P(array), &pos);
  // 遍历每个元素，并执行键<->值交换操作
  while (zend_hash_get_current_data_ex(Z_ARRVAL_P(array), (void **)&entry, &pos) == SUCCESS) {
    // 初始化一个结构体
    MAKE_STD_ZVAL(data);
    // 将原数组的值赋值为新数组的键
    switch (zend_hash_get_current_key_ex(Z_ARRVAL_P(array), &string_key, &str_key_len, &num_key, 1, &pos)) {
      case HASH_KEY_IS_STRING:
        ZVAL_STRINGL(data, string_key, str_key_len - 1, 0);
        break;
      case HASH_KEY_IS_LONG:
        Z_TYPE_P(data) = IS_LONG;
        Z_LVAL_P(data) = num_key;
        break;
    }

    // 将原数组的键赋值为新数组的值，如果有重复的，则使用新值覆盖旧值
    if (Z_TYPE_PP(entry) == IS_LONG) {
      zend_hash_index_update(Z_ARRVAL_P(return_value), Z_LVAL_PP(entry), &data, sizeof(data), NULL);
    } else if (Z_TYPE_PP(entry) == IS_STRING) {
      zend_symtable_update(Z_ARRVAL_P(return_value), Z_STRVAL_PP(entry), Z_STRLEN_PP(entry) + 1, &data, sizeof(data), NULL);
    } else {
      zval_ptr_dtor(&data); /* will free also zval structure */
      php_error_docref(NULL TSRMLS_CC, E_WARNING, "Can only flip STRING and INTEGER values!");
    }

    // 下一个
    zend_hash_move_forward_ex(Z_ARRVAL_P(array), &pos);
  }
}
/* }}} */

/* {{{ proto array array_unique(array input [, int sort_flags])
  Removes duplicate values from array */
PHP_FUNCTION(array_unique)
{
  // 定义变量
  zval *array, *tmp;
  Bucket *p;
  struct bucketindex {
    Bucket *b;
    unsigned int i;
  };
  struct bucketindex *arTmp, *cmpdata, *lastkept;
  unsigned int i;
  long sort_type = PHP_SORT_STRING;

  // 解析参数
  if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a|l", &array, &sort_type) == FAILURE) {
    return;
  }

  // 设置比较函数
  php_set_compare_func(sort_type TSRMLS_CC);

  // 初始化返回数组
  array_init_size(return_value, zend_hash_num_elements(Z_ARRVAL_P(array)));
  // 将值拷贝到新数组
  zend_hash_copy(Z_ARRVAL_P(return_value), Z_ARRVAL_P(array), (copy_ctor_func_t) zval_add_ref, (void *)&tmp, sizeof(zval*));

  if (Z_ARRVAL_P(array)->nNumOfElements <= 1) {  /* 什么都不做 */
    return;
  }

  /* 根据target_hash buckets的指针创建数组并排序 */
  arTmp = (struct bucketindex *) pemalloc((Z_ARRVAL_P(array)->nNumOfElements + 1) * sizeof(struct bucketindex), Z_ARRVAL_P(array)->persistent);
  if (!arTmp) {
    zval_dtor(return_value);
    RETURN_FALSE;
  }
  for (i = 0, p = Z_ARRVAL_P(array)->pListHead; p; i++, p = p->pListNext) {
    arTmp[i].b = p;
    arTmp[i].i = i;
  }
  arTmp[i].b = NULL;
  // 排序
  zend_qsort((void *) arTmp, i, sizeof(struct bucketindex), php_array_data_compare TSRMLS_CC);

  /* 遍历排序好的数组，然后删除重复的元素 */
  lastkept = arTmp;
  for (cmpdata = arTmp + 1; cmpdata->b; cmpdata++) {
    if (php_array_data_compare(lastkept, cmpdata TSRMLS_CC)) {
      lastkept = cmpdata;
    } else {
      if (lastkept->i > cmpdata->i) {
        p = lastkept->b;
        lastkept = cmpdata;
      } else {
        p = cmpdata->b;
      }
      if (p->nKeyLength == 0) {
        zend_hash_index_del(Z_ARRVAL_P(return_value), p->h);
      } else {
        if (Z_ARRVAL_P(return_value) == &EG(symbol_table)) {
          zend_delete_global_variable(p->arKey, p->nKeyLength - 1 TSRMLS_CC);
        } else {
          zend_hash_quick_del(Z_ARRVAL_P(return_value), p->arKey, p->nKeyLength, p->h);
        }
      }
    }
  }
  pefree(arTmp, Z_ARRVAL_P(array)->persistent);
}
/* }}} */