kk Blog —— 通用基础

<?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>';  

353352
437848
522024
argv:84.416bytes
argv:84.176bytes

<?php  
	$start = memory_get_usage();  
	$a = array_fill(0, 10000, 1);  
	$mid = memory_get_usage(); //10k elements array;  
	echo 'argv:', ($mid - $start )/10000,'byte' , '<br>';  
	$b = array_fill(0, 10000, 1);  
	$end = memory_get_usage(); //10k elements array;  
	echo 'argv:', ($end - $mid)/10000 ,'byte' , '<br>';  

argv:54.5792byte
argv:54.5784byte

#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;   
}  

int:4
long:4
double:8
har*:4
size_t:4
在PHP中都使用long类型来代表数字，没有使用int类型
大家都明白PHP是一种弱类型的语言，它不会去区分变量的类型，没有int float char *之类的概念。
我们看看php在zend里面存储的变量，PHP中每个变量都有对应的 zval， Zval结构体定义在Zend/zend.h里面，其结构:

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 order 4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;