对php内核有一定了解的人应该都知道php的精髓就是HashTable，HashTable在php的实现中无处不在。包括php的数组、什么全局变量、局部变量的作用域等等，php的hashtable拆开来说就是四部分：
hash函数：用的是time33的散列函数，将一个字符串的key转换成一个数字
一个C数组：用来储存桶(buckets)的
两个双向的链表：第一个双向链表是数组的每个元素（桶bucket）是一个双向链表，这样做是为了解决hash冲突；第二个双向链表是数组将每一个桶(bucket)连接起来，这里要连接的也就是第一个双向链表的链表头，这样做是为了遍历整个hash表用的,鸟哥有篇blog是讲php的foreach的，这里这样设计就是给foreach用的==>《深入理解PHP之数组(遍历顺序)》
我这里不再说hashtable的struct和bucket的struct了，因为下面的推荐链接几乎都讲了，我不觉得我能描述和说的比他们好，每个人的水平不一样，我就以我现在的技术水平来描述，所以我就只把我整理的一些东西记录一下
下面是php中hash实现的两个文件：zend_hash.c zend_hash.h。这两个文件里面实现了一堆的api，也引申出了一堆的api，下面是实现出来的api的原型
代码如下:
ZEND_API ulong zend_hash_func(const char *arKey, uint nKeyLength)
ZEND_API ulong zend_get_hash_value(const char *arKey, uint nKeyLength)
ZEND_API int _zend_hash_init(HashTable *ht, uint nSize, hash_func_t pHashFunction, dtor_func_t pDestructor, zend_bool persistent ZEND_FILE_LINE_DC)
ZEND_API void zend_hash_set_apply_protection(HashTable *ht, zend_bool bApplyProtection)
ZEND_API int _zend_hash_add_or_update(HashTable *ht, const char *arKey, uint nKeyLength, void *pData, uint nDataSize, void **pDest, int flag ZEND_FILE_LINE_DC)
ZEND_API int _zend_hash_quick_add_or_update(HashTable *ht, const char *arKey, uint nKeyLength, ulong h, void *pData, uint nDataSize, void **pDest, int flag ZEND_FILE_LINE_DC)
ZEND_API int _zend_hash_index_update_or_next_insert(HashTable *ht, ulong h, void *pData, uint nDataSize, void **pDest, int flag ZEND_FILE_LINE_DC)
ZEND_API int zend_hash_rehash(HashTable *ht)
static int zend_hash_do_resize(HashTable *ht)
ZEND_API int zend_hash_del_key_or_index(HashTable *ht, const char *arKey, uint nKeyLength, ulong h, int flag)
ZEND_API void zend_hash_destroy(HashTable *ht)
ZEND_API void zend_hash_clean(HashTable *ht)
static Bucket *zend_hash_apply_deleter(HashTable *ht, Bucket *p)
ZEND_API void zend_hash_graceful_destroy(HashTable *ht)
ZEND_API void zend_hash_graceful_reverse_destroy(HashTable *ht)
ZEND_API void zend_hash_apply(HashTable *ht, apply_func_t apply_func TSRMLS_DC)
ZEND_API void zend_hash_apply_with_argument(HashTable *ht, apply_func_arg_t apply_func, void *argument TSRMLS_DC)
ZEND_API void zend_hash_apply_with_arguments(HashTable *ht TSRMLS_DC, apply_func_args_t apply_func, int num_args, …)
ZEND_API void zend_hash_reverse_apply(HashTable *ht, apply_func_t apply_func TSRMLS_DC)
ZEND_API void zend_hash_copy(HashTable *target, HashTable *source, copy_ctor_func_t pCopyConstructor, void *tmp, uint size)
ZEND_API void _zend_hash_merge(HashTable *target, HashTable *source, copy_ctor_func_t pCopyConstructor, void *tmp, uint size, int overwrite ZEND_FILE_LINE_DC)
static zend_bool zend_hash_replace_checker_wrapper(HashTable *target, void *source_data, Bucket *p, void *pParam, merge_checker_func_t merge_checker_func)
ZEND_API void zend_hash_merge_ex(HashTable *target, HashTable *source, copy_ctor_func_t pCopyConstructor, uint size, merge_checker_func_t pMergeSource, void *pParam)
ZEND_API int zend_hash_find(const HashTable *ht, const char *arKey, uint nKeyLength, void **pData)
ZEND_API int zend_hash_quick_find(const HashTable *ht, const char *arKey, uint nKeyLength, ulong h, void **pData)
ZEND_API int zend_hash_exists(const HashTable *ht, const char *arKey, uint nKeyLength)
ZEND_API int zend_hash_quick_exists(const HashTable *ht, const char *arKey, uint nKeyLength, ulong h)
ZEND_API int zend_hash_index_find(const HashTable *ht, ulong h, void **pData)
ZEND_API int zend_hash_index_exists(const HashTable *ht, ulong h)
ZEND_API int zend_hash_num_elements(const HashTable *ht)
ZEND_API int zend_hash_get_pointer(const HashTable *ht, HashPointer *ptr)
ZEND_API int zend_hash_set_pointer(HashTable *ht, const HashPointer *ptr)
ZEND_API void zend_hash_internal_pointer_reset_ex(HashTable *ht, HashPosition *pos)
ZEND_API void zend_hash_internal_pointer_end_ex(HashTable *ht, HashPosition *pos)
ZEND_API int zend_hash_move_forward_ex(HashTable *ht, HashPosition *pos)
ZEND_API int zend_hash_move_backwards_ex(HashTable *ht, HashPosition *pos)
ZEND_API int zend_hash_get_current_key_ex(const HashTable *ht, char **str_index, uint *str_length, ulong *num_index, zend_bool duplicate, HashPosition *pos)
ZEND_API int zend_hash_get_current_key_type_ex(HashTable *ht, HashPosition *pos)
ZEND_API int zend_hash_get_current_data_ex(HashTable *ht, void **pData, HashPosition *pos)
ZEND_API int zend_hash_update_current_key_ex(HashTable *ht, int key_type, const char *str_index, uint str_length, ulong num_index, int mode, HashPosition *pos)
ZEND_API int zend_hash_sort(HashTable *ht, sort_func_t sort_func, compare_func_t compar, int renumber TSRMLS_DC)
ZEND_API int zend_hash_compare(HashTable *ht1, HashTable *ht2, compare_func_t compar, zend_bool ordered TSRMLS_DC)
ZEND_API int zend_hash_minmax(const HashTable *ht, compare_func_t compar, int flag, void **pData TSRMLS_DC)
ZEND_API ulong zend_hash_next_free_element(const HashTable *ht)
void zend_hash_display_pListTail(const HashTable *ht)
void zend_hash_display(const HashTable *ht)