PHP数组实际占用内存大小原理解析

<?php 
  echo memory_get_usage() , '<br>'; 
  $start = memory_get_usage(); 
  $a = Array(); 
  for ($i=0; $i<1000; $i++) { 
  $a[$i] = $i + $i; 
  } 
  $mid = memory_get_usage(); 
  echo memory_get_usage() , '<br>'; 
  for ($i=1000; $i<2000; $i++) { 
  $a[$i] = $i + $i; 
  } 
  $end = memory_get_usage(); 
  echo memory_get_usage() , '<br>'; 
  echo 'argv:', ($mid - $start)/1000 ,'bytes' , '<br>'; 
  echo 'argv:',($end - $mid)/1000 ,'bytes' , '<br>'; 

#include "stdafx.h" 
//#include <stdio.h> 
  
int main() { 
    printf("int:%d\nlong:%d\ndouble:%d\nchar*:%d\nsize_t:%d\n",  
    sizeof(int), sizeof(long),  
    sizeof(double), sizeof(char *),  
    sizeof(size_t)); 
  return  0;  
} 

typedef struct _zval_struct zval; 
struct _zval_struct { 
  /* Variable information */ 
  zvalue_value value;   /* The value 1 12字节(32位机是12，64位机需要8+4+4=16) */ 
  zend_uint refcount__gc; /* The number of references to this value (for GC) 4字节 */ 
  zend_uchar type;    /* The active type 1字节*/ 
  zend_uchar is_ref__gc; /* Whether this value is a reference (&) 1字节*/ 
}; 

typedef union _zvalue_value { 
  long lval;         /* long value */ 
  double dval;        /* double value */ 
  struct {          /* string value */ 
    char *val; 
    int len; 
  } str;  
  HashTable *ht;       /* hash table value */ 
  zend_object_value obj;   /*object value */ 
} zvalue_value; 

typedef struct _hashtable { 
  uint nTableSize;//4 
  uint nTableMask;//4 
  uint nNumOfElements;//4 
  ulong nNextFreeElement;//4 
  Bucket *pInternalPointer;  /* Used for element traversal 4*/ 
  Bucket *pListHead;//4 
  Bucket *pListTail;//4 
  Bucket **arBuckets;//4 
  dtor_func_t pDestructor;//4 
  zend_bool persistent;//1 
  unsigned char nApplyCount;//1 
  zend_bool bApplyProtection;//1 
#if ZEND_DEBUG 
  int inconsistent;//4 
#endif 
} HashTable; 

typedef struct bucket { 
  ulong h;  /* Used for numeric indexing        4字节 */ 
  uint nKeyLength;  /* The length of the key (for string keys) 4字节 */ 
  void *pData;    /* 4字节*/ 
  void *pDataPtr;     /* 4字节*/ 
  struct bucket *pListNext; /* PHP arrays are ordered. This gives the next element in that order4字节*/ 
  struct bucket *pListLast; /* and this gives the previous element      4字节 */ 
  struct bucket *pNext;   /* The next element in this (doubly) linked list   4字节*/ 
  struct bucket *pLast;   /* The previous element in this (doubly) linked list   4字节*/ 
  char arKey[1];      /* Must be last element  1字节*/ 
} Bucket;