【PHP内核学习】变量和数据类型
<div class="line" id="LC1" style="padding-left:10px; height:18px">|=-----------------------------------------------------------------------=|<div class="line" id="LC2" style="padding-left:10px; height:18px">|=---------------------=[ PHP内核中的变量和数据类型]=--------------------=|<div class="line" id="LC3" style="padding-left:10px; height:18px">|=-----------------------------------------------------------------------=|<div class="line" id="LC4" style="padding-left:10px; height:18px">|=--------------------------=[ by d4shman ]=-----------------------------=|<div class="line" id="LC5" style="padding-left:10px; height:18px">|=-----------------------------------------------------------------------=|<div class="line" id="LC6" style="padding-left:10px; height:18px">|=-------------------------=[ May 6, 2014 ]=---------------------------=|<div class="line" id="LC7" style="padding-left:10px; height:18px">|=-----------------------------------------------------------------------=|<div class="line" id="LC8" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC9" style="padding-left:10px; height:18px">(_____ \| | | (_____ \ /\ / _____) | / ) <div class="line" id="LC10" style="padding-left:10px; height:18px"> _____) ) |__ | |_____) ) / \ | / | | / / <div class="line" id="LC11" style="padding-left:10px; height:18px">| ____/| __)| (_____ ( / /\ \| | | |<div class="line" id="LC12" style="padding-left:10px; height:18px">| | | | | | | | |__| | \_____| | \ \ <div class="line" id="LC13" style="padding-left:10px; height:18px">|_| |_| |_| |_|______|\______)_| \_) (向phrack致敬!)<div class="line" id="LC14" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC15" style="padding-left:10px; height:18px"><div class="line" id="LC16" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC17" style="padding-left:10px; height:18px"> 0x01 变量的结构和类型<div class="line" id="LC18" style="padding-left:10px; height:18px"> 0x02 哈希表--PHP的灵魂<div class="line" id="LC19" style="padding-left:10px; height:18px"> 0x03 常量<div class="line" id="LC20" style="padding-left:10px; height:18px"> 0x04 参考文献<div class="line" id="LC21" style="padding-left:10px; height:18px"><div class="line" id="LC22" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC23" style="padding-left:10px; height:18px">/////<div class="line" id="LC24" style="padding-left:10px; height:18px">0x01 变量的结构和类型<div class="line" id="LC25" style="padding-left:10px; height:18px">/////<div class="line" id="LC26" style="padding-left:10px; height:18px">1.数据类型<div class="line" id="LC27" style="padding-left:10px; height:18px"> 1.1静态类型语言（C/Java）,编译时确定<div class="line" id="LC28" style="padding-left:10px; height:18px"> 1.2动态类型语言（php/python）,运行时确定<div class="line" id="LC29" style="padding-left:10px; height:18px"> 1.3无类型语言(汇编)，操作的底层存储<div class="line" id="LC30" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC31" style="padding-left:10px; height:18px">2.php内核中所有的变量使用同一种数据结构zval来保存，而这个结构同时表示php中各种数据类型，它不仅仅包含变量的值，也包含变量的类型。这就是php弱类型的核心。<div class="line" id="LC32" style="padding-left:10px; height:18px"> php中的8中数据类型：<div class="line" id="LC33" style="padding-left:10px; height:18px"> 2.1标量类型： boolean, integer, float, string<div class="line" id="LC34" style="padding-left:10px; height:18px"> 2.2复合类型: array, object<div class="line" id="LC35" style="padding-left:10px; height:18px"> 2.3特殊类型： resource, null<div class="line" id="LC36" style="padding-left:10px; height:18px"> <div class="line" id="LC37" style="padding-left:10px; height:18px">3.zval结构体(在php源码目录下Zend/zend.h中定义)：<div class="line" id="LC38" style="padding-left:10px; height:18px"> struct _zval_struct｛<div class="line" id="LC39" style="padding-left:10px; height:18px"> /*Variable information*/<div class="line" id="LC40" style="padding-left:10px; height:18px"> zvalue_value value /*value， 变量的值*/<div class="line" id="LC41" style="padding-left:10px; height:18px"> zend_uint refcount__gc /*reference count， 引用计数器*/<div class="line" id="LC42" style="padding-left:10px; height:18px"> zend_uchar type /*active type， 变量的类型*/<div class="line" id="LC43" style="padding-left:10px; height:18px"> zend_uchar is_ref__gc; /*变量是否被引用*/<div class="line" id="LC44" style="padding-left:10px; height:18px"> ｝<div class="line" id="LC45" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC46" style="padding-left:10px; height:18px">4.变量类型：<div class="line" id="LC47" style="padding-left:10px; height:18px"> /*data types */<div class="line" id="LC48" style="padding-left:10px; height:18px"> #define IS_NULL 0 <div class="line" id="LC49" style="padding-left:10px; height:18px"> #define IS_LONG 1<div class="line" id="LC50" style="padding-left:10px; height:18px"> #define IS_DOUBLE 2<div class="line" id="LC51" style="padding-left:10px; height:18px"> #define IS_BOOL 3<div class="line" id="LC52" style="padding-left:10px; height:18px"> #define IS_ARRAY 4<div class="line" id="LC53" style="padding-left:10px; height:18px"> #define IS_OBJECT 5<div class="line" id="LC54" style="padding-left:10px; height:18px"> #define IS_STRING 6<div class="line" id="LC55" style="padding-left:10px; height:18px"> #define IS_RESOURCE 7<div class="line" id="LC56" style="padding-left:10px; height:18px"> #define IS_CONSTANT 8<div class="line" id="LC57" style="padding-left:10px; height:18px"> #define IS_CONSTANT_ARRAY 9<div class="line" id="LC58" style="padding-left:10px; height:18px"> #define IS_CALLABLE 10<div class="line" id="LC59" style="padding-left:10px; height:18px"> <div class="line" id="LC60" style="padding-left:10px; height:18px">5.变量的值存储<div class="line" id="LC61" style="padding-left:10px; height:18px"> typedef union _zvalue_value {<div class="line" id="LC62" style="padding-left:10px; height:18px"> long lval; /*long、bool、resource类型*/<div class="line" id="LC63" style="padding-left:10px; height:18px"> double dval ; /*double 类型*/<div class="line" id="LC64" style="padding-left:10px; height:18px"> struct { /*string 类型, len保存了字符串的长度*/<div class="line" id="LC65" style="padding-left:10px; height:18px"> char *val;<div class="line" id="LC66" style="padding-left:10px; height:18px"> int len;<div class="line" id="LC67" style="padding-left:10px; height:18px"> } str;<div class="line" id="LC68" style="padding-left:10px; height:18px"> HashTable *ht; /*数组, 用HashTable实现*/<div class="line" id="LC69" style="padding-left:10px; height:18px"> zend_object_value obj; /*object 类型*/<div class="line" id="LC70" style="padding-left:10px; height:18px"> } zvalue_value;<div class="line" id="LC71" style="padding-left:10px; height:18px"> <div class="line" id="LC72" style="padding-left:10px; height:18px"> 这里之所以用共同体(union)是因为一个变量只可能有一种类型，符合共同体的特性，如果使用结构体则会浪费内存。<div class="line" id="LC73" style="padding-left:10px; height:18px"> <div class="line" id="LC74" style="padding-left:10px; height:18px"> 实例：创建一个值为10的整型变量lvar,用php脚本的话很简单，就是:$lvar = 10<div class="line" id="LC75" style="padding-left:10px; height:18px"> 而PHP内核中的实现可能就是类似下面这样：<div class="line" id="LC76" style="padding-left:10px; height:18px"> zval lval;<div class="line" id="LC77" style="padding-left:10px; height:18px"> Z_TYPE(lvar) = IS_LONG;<div class="line" id="LC78" style="padding-left:10px; height:18px"> Z_LVAL(lvar) = 10;<div class="line" id="LC79" style="padding-left:10px; height:18px"> <div class="line" id="LC80" style="padding-left:10px; height:18px">/////<div class="line" id="LC81" style="padding-left:10px; height:18px">0x02 哈希表--PHP的灵魂<div class="line" id="LC82" style="padding-left:10px; height:18px">/////<div class="line" id="LC83" style="padding-left:10px; height:18px">1.为什么用哈希表<div class="line" id="LC84" style="padding-left:10px; height:18px"> 哈希表通常提供CRUD(Create, Read, Update, Delete)操作，设计合理的哈希表中，这些操作时间复杂度为O(1)，这也是它被钟爱的原因。<div class="line" id="LC85" style="padding-left:10px; height:18px"> hash(key) -> index<div class="line" id="LC86" style="padding-left:10px; height:18px"> <div class="line" id="LC87" style="padding-left:10px; height:18px">2.哈希表的实现：结构体 bucket和_hashtable组成了完整的HashTable。<div class="line" id="LC88" style="padding-left:10px; height:18px"> 首先看bucket结构体(定义在 Zend/zend_hash.h):<div class="line" id="LC89" style="padding-left:10px; height:18px"> typedef struct bucket {<div class="line" id="LC90" style="padding-left:10px; height:18px"> ulong h; /*hash值*/<div class="line" id="LC91" style="padding-left:10px; height:18px"> uint nKeyLength; /*key的长度*/<div class="line" id="LC92" style="padding-left:10px; height:18px"> void *pData; /*要保存的内存块地址，通常是malloc来的地址*/<div class="line" id="LC93" style="padding-left:10px; height:18px"> void *pDataPtr; /*保存指针数据，不经过malloc的指针，防止产生内存碎片*/<div class="line" id="LC94" style="padding-left:10px; height:18px"> struct bucket *pListNext; /*bucket中具有同一hash值的下一个元素*/<div class="line" id="LC95" style="padding-left:10px; height:18px"> struct bucket *pListLast; /*bucket中具有同一hash值的上一个元素*/<div class="line" id="LC96" style="padding-left:10px; height:18px"> struct bucket *pNext; /*双向链表的下一个元素*/<div class="line" id="LC97" style="padding-left:10px; height:18px"> struct bucket *pLast; /*双向链表的上一个元素*/<div class="line" id="LC98" style="padding-left:10px; height:18px"> const char *arKey; /*保存key*/<div class="line" id="LC99" style="padding-left:10px; height:18px"> } Bucket;<div class="line" id="LC100" style="padding-left:10px; height:18px"> <div class="line" id="LC101" style="padding-left:10px; height:18px"> 可以看出bucket是一个双向链表，这是为了解决多个key冲突的问题(即算法导论中的链接法)<div class="line" id="LC102" style="padding-left:10px; height:18px"> <div class="line" id="LC103" style="padding-left:10px; height:18px"> <div class="line" id="LC104" style="padding-left:10px; height:18px"> 再看_hashtable结构体：<div class="line" id="LC105" style="padding-left:10px; height:18px"> typedef struct _hashtable {<div class="line" id="LC106" style="padding-left:10px; height:18px"> uint nTableSize; /*bucket数组的大小*/<div class="line" id="LC107" style="padding-left:10px; height:18px"> uint nTableMask; <div class="line" id="LC108" style="padding-left:10px; height:18px"> uint nNumOfElements; /*HashTable中元素的个数*/<div class="line" id="LC109" style="padding-left:10px; height:18px"> ulong nNextFreeElement; /*下一个可用的Bucket位置*/<div class="line" id="LC110" style="padding-left:10px; height:18px"> Bucket *pInternalPointer /*遍历HashTable元素*/<div class="line" id="LC111" style="padding-left:10px; height:18px"> Bucket *pListHead; /*双向链表表头*/<div class="line" id="LC112" style="padding-left:10px; height:18px"> Bucket *pListTail; /*双向链表表尾*/<div class="line" id="LC113" style="padding-left:10px; height:18px"> Bucket **arBuckets; /*Bucket数组*/<div class="line" id="LC114" style="padding-left:10px; height:18px"> } HashTable;<div class="line" id="LC115" style="padding-left:10px; height:18px"> <div class="line" id="LC116" style="padding-left:10px; height:18px"> ========<div class="line" id="LC117" style="padding-left:10px; height:18px"> 此处为HashTable的结构图<div class="line" id="LC118" style="padding-left:10px; height:18px"> ========<div class="line" id="LC119" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC120" style="padding-left:10px; height:18px">3.神奇的数字--33<div class="line" id="LC121" style="padding-left:10px; height:18px"> 见我原来的一篇博客：http://blog.csdn.net/wusuopubupt/article/details/11479869<div class="line" id="LC122" style="padding-left:10px; height:18px"> 下面是PHP源码中的一段注释：<div class="line" id="LC123" style="padding-left:10px; height:18px"> /*<div class="line" id="LC124" style="padding-left:10px; height:18px"> * DJBX33A (Daniel J. Bernstein, Times 33 with Addition)<div class="line" id="LC125" style="padding-left:10px; height:18px"> *<div class="line" id="LC126" style="padding-left:10px; height:18px"> * This is Daniel J. Bernstein's popular `times 33' hash function as<div class="line" id="LC127" style="padding-left:10px; height:18px"> * posted by him years ago on comp.lang.c. It basically uses a function<div class="line" id="LC128" style="padding-left:10px; height:18px"> * like ``hash(i) = hash(i-1) * 33 + str[i]''. This is one of the best<div class="line" id="LC129" style="padding-left:10px; height:18px"> * known hash functions for strings. Because it is both computed very<div class="line" id="LC130" style="padding-left:10px; height:18px"> * fast and distributes very well.<div class="line" id="LC131" style="padding-left:10px; height:18px"> *<div class="line" id="LC132" style="padding-left:10px; height:18px"> * The magic of number 33, i.e. why it works better than many other<div class="line" id="LC133" style="padding-left:10px; height:18px"> * constants, prime or not, has never been adequately explained by<div class="line" id="LC134" style="padding-left:10px; height:18px"> * anyone. So I try an explanation: if one experimentally tests all<div class="line" id="LC135" style="padding-left:10px; height:18px"> * multipliers between 1 and 256 (as RSE did now) one detects that even<div class="line" id="LC136" style="padding-left:10px; height:18px"> * numbers are not useable at all. The remaining 128 odd numbers<div class="line" id="LC137" style="padding-left:10px; height:18px"> * (except for the number 1) work more or less all equally well. They<div class="line" id="LC138" style="padding-left:10px; height:18px"> * all distribute in an acceptable way and this way fill a hash table<div class="line" id="LC139" style="padding-left:10px; height:18px"> * with an average percent of approx. 86%.<div class="line" id="LC140" style="padding-left:10px; height:18px"> *<div class="line" id="LC141" style="padding-left:10px; height:18px"> * If one compares the Chi^2 values of the variants, the number 33 not<div class="line" id="LC142" style="padding-left:10px; height:18px"> * even has the best value. But the number 33 and a few other equally<div class="line" id="LC143" style="padding-left:10px; height:18px"> * good numbers like 17, 31, 63, 127 and 129 have nevertheless a great<div class="line" id="LC144" style="padding-left:10px; height:18px"> * advantage to the remaining numbers in the large set of possible<div class="line" id="LC145" style="padding-left:10px; height:18px"> * multipliers: their multiply operation can be replaced by a faster<div class="line" id="LC146" style="padding-left:10px; height:18px"> * operation based on just one shift plus either a single addition<div class="line" id="LC147" style="padding-left:10px; height:18px"> * or subtraction operation. And because a hash function has to both<div class="line" id="LC148" style="padding-left:10px; height:18px"> * distribute good _and_ has to be very fast to compute, those few<div class="line" id="LC149" style="padding-left:10px; height:18px"> * numbers should be preferred and seems to be the reason why Daniel J.<div class="line" id="LC150" style="padding-left:10px; height:18px"> * Bernstein also preferred it.<div class="line" id="LC151" style="padding-left:10px; height:18px"> *<div class="line" id="LC152" style="padding-left:10px; height:18px"> *<div class="line" id="LC153" style="padding-left:10px; height:18px"> * -- Ralf S. Engelschall <div class="line" id="LC154" style="padding-left:10px; height:18px"> */<div class="line" id="LC155" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC156" style="padding-left:10px; height:18px"> <div class="line" id="LC157" style="padding-left:10px; height:18px">4.哈希表的操作接口(省略了部分参数)<div class="line" id="LC158" style="padding-left:10px; height:18px"> 初始化HashTable：int _zend_hash_init(HashTable *ht, uint nSize, hash_func_t pHashFunction);<div class="line" id="LC159" style="padding-left:10px; height:18px"> 添加新hash值： int _zend_hash_add_or_update(HashTable *ht, const char *arKey, uint nKeyLength, void *pData)<div class="line" id="LC160" style="padding-left:10px; height:18px"> 查找hash： int zend_hash_find(const HashTable *ht, const char *arKey, uint nKeyLength, void **pData);<div class="line" id="LC161" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC162" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC163" style="padding-left:10px; height:18px">/////<div class="line" id="LC164" style="padding-left:10px; height:18px">0x03 常量<div class="line" id="LC165" style="padding-left:10px; height:18px">///// <div class="line" id="LC166" style="padding-left:10px; height:18px">1.常量的内部结构<div class="line" id="LC167" style="padding-left:10px; height:18px"> typedef struct _zend_constant {<div class="line" id="LC168" style="padding-left:10px; height:18px"> zval value;<div class="line" id="LC169" style="padding-left:10px; height:18px"> int flags; /*常量标记，如 CONST_PERSISTENT | CONST_CS */<div class="line" id="LC170" style="padding-left:10px; height:18px"> char *name;<div class="line" id="LC171" style="padding-left:10px; height:18px"> uint name_len;<div class="line" id="LC172" style="padding-left:10px; height:18px"> int module_number;<div class="line" id="LC173" style="padding-left:10px; height:18px"> } zend_constant;<div class="line" id="LC174" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC175" style="padding-left:10px; height:18px">2.define定义常量的过程 <div class="line" id="LC176" style="padding-left:10px; height:18px"> define的实现(定义在Zend/zend_builtin_functions.c)，下面是部分核心代码：<div class="line" id="LC177" style="padding-left:10px; height:18px"> <div class="line" id="LC178" style="padding-left:10px; height:18px"> ZEND_FUNCTION(define)<div class="line" id="LC179" style="padding-left:10px; height:18px"> {<div class="line" id="LC180" style="padding-left:10px; height:18px"> /* 检查常量名是否存在 */<div class="line" id="LC181" style="padding-left:10px; height:18px"> if (zend_memnstr(name, "::", sizeof("::") - 1, name + name_len)) {<div class="line" id="LC182" style="padding-left:10px; height:18px"> zend_error(E_WARNING, "Class constants cannot be defined or redefined");<div class="line" id="LC183" style="padding-left:10px; height:18px"> RETURN_FALSE;<div class="line" id="LC184" style="padding-left:10px; height:18px"> }<div class="line" id="LC185" style="padding-left:10px; height:18px"> <div class="line" id="LC186" style="padding-left:10px; height:18px"> ... // 类常量定义 此处不做介绍<div class="line" id="LC187" style="padding-left:10px; height:18px"> <div class="line" id="LC188" style="padding-left:10px; height:18px"> c.value = *val;<div class="line" id="LC189" style="padding-left:10px; height:18px"> zval_copy_ctor(&c.value);<div class="line" id="LC190" style="padding-left:10px; height:18px"> if (val_free) {<div class="line" id="LC191" style="padding-left:10px; height:18px"> zval_ptr_dtor(&val_free);<div class="line" id="LC192" style="padding-left:10px; height:18px"> }<div class="line" id="LC193" style="padding-left:10px; height:18px"> c.flags = case_sensitive; /* 大小写敏感 */<div class="line" id="LC194" style="padding-left:10px; height:18px"> c.name = zend_strndup(name, name_len);<div class="line" id="LC195" style="padding-left:10px; height:18px"> c.name_len = name_len+1;<div class="line" id="LC196" style="padding-left:10px; height:18px"> c.module_number = PHP_USER_CONSTANT;<div class="line" id="LC197" style="padding-left:10px; height:18px"> if (zend_register_constant(&c TSRMLS_CC) == SUCCESS) { /*注册常量*/<div class="line" id="LC198" style="padding-left:10px; height:18px"> RETURN_TRUE;<div class="line" id="LC199" style="padding-left:10px; height:18px"> } else {<div class="line" id="LC200" style="padding-left:10px; height:18px"> RETURN_FALSE;<div class="line" id="LC201" style="padding-left:10px; height:18px"> }<div class="line" id="LC202" style="padding-left:10px; height:18px"> }<div class="line" id="LC203" style="padding-left:10px; height:18px"> <div class="line" id="LC204" style="padding-left:10px; height:18px">3.魔术常量<div class="line" id="LC205" style="padding-left:10px; height:18px"> PHP中的魔术常量，虽然叫做常量，但它们的值实际上随它们在代码中的位置而变化的。<div class="line" id="LC206" style="padding-left:10px; height:18px"> __LINE__ 文件中的当前行号。<div class="line" id="LC207" style="padding-left:10px; height:18px"> __FILE__ 文件的完整路径和文件名。如果用在被包含文件中，则返回被包含的文件名。<div class="line" id="LC208" style="padding-left:10px; height:18px"> __DIR__ 文件所在的目录。如果用在被包括文件中，则返回被包括的文件所在的目录。它等价于 dirname(__FILE__)。<div class="line" id="LC209" style="padding-left:10px; height:18px"> __FUNCTION__ 函数名称<div class="line" id="LC210" style="padding-left:10px; height:18px"> __CLASS__ 类的名称。类名包括其被声明的作用区域（例如 Foo\Bar）。<div class="line" id="LC211" style="padding-left:10px; height:18px"> __TRAIT__ Trait 的名字。Trait 名包括其被声明的作用区域（例如 Foo\Bar）。<div class="line" id="LC212" style="padding-left:10px; height:18px"> __METHOD__ 类的方法名<div class="line" id="LC213" style="padding-left:10px; height:18px"> __NAMESPACE__ 当前命名空间的名称（区分大小写）。此常量是在编译时定义的（PHP 5.3.0 新增）。<div class="line" id="LC214" style="padding-left:10px; height:18px"> <div class="line" id="LC215" style="padding-left:10px; height:18px"> PHP内核会在词法解析时将这些常量的内容赋值进行替换，而不是在运行时进行分析。 举个例子：<div class="line" id="LC216" style="padding-left:10px; height:18px"> <?php </p><div class="line" id="LC217" style="padding-left:10px; height:18px"> echo __LINE__;<div class="line" id="LC218" style="padding-left:10px; height:18px"> function demo() {<div class="line" id="LC219" style="padding-left:10px; height:18px"> echo __FUNCTION__;<div class="line" id="LC220" style="padding-left:10px; height:18px"> }<div class="line" id="LC221" style="padding-left:10px; height:18px"> demo();<div class="line" id="LC222" style="padding-left:10px; height:18px"> ?><div class="line" id="LC223" style="padding-left:10px; height:18px"> PHP已经在词法解析时将这些常量换成了对应的值，以上的代码可以看成如下的PHP代码：<div class="line" id="LC224" style="padding-left:10px; height:18px"> <?php </p><div class="line" id="LC225" style="padding-left:10px; height:18px"> echo 2;<div class="line" id="LC226" style="padding-left:10px; height:18px"> function demo() {<div class="line" id="LC227" style="padding-left:10px; height:18px"> echo "demo";<div class="line" id="LC228" style="padding-left:10px; height:18px"> }<div class="line" id="LC229" style="padding-left:10px; height:18px"> demo();<div class="line" id="LC230" style="padding-left:10px; height:18px"> ?><div class="line" id="LC231" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC232" style="padding-left:10px; height:18px"> ===========<div class="line" id="LC233" style="padding-left:10px; height:18px"> 此处涉及编译原理知识，需补充。<div class="line" id="LC234" style="padding-left:10px; height:18px"> ===========<div class="line" id="LC235" style="padding-left:10px; height:18px"> <div class="line" id="LC236" style="padding-left:10px; height:18px">/////<div class="line" id="LC237" style="padding-left:10px; height:18px">0x04 参考文献<div class="line" id="LC238" style="padding-left:10px; height:18px">///// <div class="line" id="LC239" style="padding-left:10px; height:18px">
<br ><div class="line" id="LC240" style="padding-left:10px; height:18px">TIPI: http://www.php-internals.com/book/?p=chapt03/03-00-variable-and-data-types<dl class="comment_item comment_topic">
<dt class="comment_head">1楼<span class="user">wusuopuBUPT<span class="ptime">昨天 14:06</span></span>
</dt>
<dd class="comment_body">本文github地址：https://github.com/wusuopubupt/phpLib/blob/master/PHP%E5%86%85%E6%A0%B8%E4%B8%AD%E7%9A%84%E5%8F%98%E9%87%8F%E5%92%8C%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B</dd>
</dl>
<div class="clear">
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div></div>
</div>
</div>
</div>
</div>
</div></div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>声明
本文内容由网友自发贡献，版权归原作者所有，本站不承担相应法律责任。如您发现有涉嫌抄袭侵权的内容，请联系admin@php.cn
优化PHP代码：减少内存使用和执行时间May 10, 2025 am 12:04 AMTOOPTIMIZEPHPCODEFORDUSEMEMORYUSAGEAGEAGEAGEAGEAGEANDEXECUTITIEM，关注台词：1）USEREEREFERESCENCENCINCOPYINSTEADOFCOPYINGINATATASTRUCTURESTROUCTURESTOREDUCEMORYCONSUMPTION.2）杠杆phphppphpphp'sbuilt intimpunctionslikearray_mapforfunctionslikearray_mapforfforfforfforfasterapasterexecution.3）
PHP电子邮件：分步发送指南May 09, 2025 am 12:14 AMphpisusedforsendendemailsduetoitsignegrationwithservermailservicesand andexternalsmtpproviders，自动化notifications andMarketingCampaigns.1）设置设置yourphpenvironcormentswironmentswithaweberswithawebserverserverserverandphp，确保themailfunctionisenabled.2）useabasicscruct
如何通过PHP发送电子邮件：示例和代码May 09, 2025 am 12:13 AM发送电子邮件的最佳方法是使用PHPMailer库。1)使用mail()函数简单但不可靠，可能导致邮件进入垃圾邮件或无法送达。2)PHPMailer提供更好的控制和可靠性，支持HTML邮件、附件和SMTP认证。3)确保正确配置SMTP设置并使用加密（如STARTTLS或SSL/TLS）以增强安全性。4)对于大量邮件，考虑使用邮件队列系统来优化性能。
高级PHP电子邮件：自定义标题和功能May 09, 2025 am 12:13 AMCustomHeadersheadersandAdvancedFeaturesInphpeMailenHanceFunctionalityAndreliability.1）CustomHeadersheadersheadersaddmetadatatatatataatafortrackingandCategorization.2）htmlemailsallowformattingandttinganditive.3）attachmentscanmentscanmentscanbesmentscanbestmentscanbesentscanbesentingslibrarieslibrarieslibrariesliblarikelikephpmailer.4）smtppapapairatienticationaltication enterticationallimpr
使用PHP和SMTP发送电子邮件的指南May 09, 2025 am 12:06 AM使用PHP和SMTP发送邮件可以通过PHPMailer库实现。1)安装并配置PHPMailer，2)设置SMTP服务器细节，3)定义邮件内容，4)发送邮件并处理错误。使用此方法可以确保邮件的可靠性和安全性。
使用PHP发送电子邮件的最佳方法是什么？May 08, 2025 am 12:21 AMThebestapproachforsendingemailsinPHPisusingthePHPMailerlibraryduetoitsreliability,featurerichness,andeaseofuse.PHPMailersupportsSMTP,providesdetailederrorhandling,allowssendingHTMLandplaintextemails,supportsattachments,andenhancessecurity.Foroptimalu
PHP中依赖注入的最佳实践May 08, 2025 am 12:21 AM使用依赖注入(DI)的原因是它促进了代码的松耦合、可测试性和可维护性。1)使用构造函数注入依赖，2)避免使用服务定位器，3)利用依赖注入容器管理依赖，4)通过注入依赖提高测试性，5)避免过度注入依赖，6)考虑DI对性能的影响。
PHP性能调整技巧和技巧May 08, 2025 am 12:20 AMphperformancetuningiscialbecapeitenhancesspeedandeffice，whatevitalforwebapplications.1）cachingwithapcureduccureducesdatabaseloadprovesrovesponsemetimes.2）优化
热AI工具
Undresser.AI Undress
人工智能驱动的应用程序，用于创建逼真的裸体照片
AI Clothes Remover
用于从照片中去除衣服的在线人工智能工具。
Undress AI Tool
免费脱衣服图片
Clothoff.io
AI脱衣机
Video Face Swap
使用我们完全免费的人工智能换脸工具轻松在任何视频中换脸！
热门文章
<🎜>：种植花园 - 完整的突变指南
3 周前ByDDD
<🎜>：泡泡胶模拟器无穷大 - 如何获取和使用皇家钥匙
3 周前By尊渡假赌尊渡假赌尊渡假赌
如何修复KB5055612无法在Windows 10中安装？
3 周前ByDDD
蓝王子：如何到达地下室
1 个月前ByDDD
北端：融合系统，解释
3 周前By尊渡假赌尊渡假赌尊渡假赌
热工具
mPDF
mPDF是一个PHP库，可以从UTF-8编码的HTML生成PDF文件。原作者Ian Back编写mPDF以从他的网站上“即时”输出PDF文件，并处理不同的语言。与原始脚本如HTML2FPDF相比，它的速度较慢，并且在使用Unicode字体时生成的文件较大，但支持CSS样式等，并进行了大量增强。支持几乎所有语言，包括RTL（阿拉伯语和希伯来语）和CJK（中日韩）。支持嵌套的块级元素（如P、DIV），
螳螂BT
Mantis是一个易于部署的基于Web的缺陷跟踪工具，用于帮助产品缺陷跟踪。它需要PHP、MySQL和一个Web服务器。请查看我们的演示和托管服务。
Atom编辑器mac版下载
最流行的的开源编辑器
SublimeText3 Mac版
神级代码编辑软件(SublimeText3)
SublimeText3汉化版
中文版，非常好用
