有一段时间一直迷惑于PHP中引用的传递，后来查手册及C源程序，并反复测试，大致对引用传递在内存中的模式有了一定的了解，后来为了加深印象，写了个总结，应该不会有大的问题——当然这是在PHP4中，在以后的版本中可能会有变化。当时写总结的时候，想锻炼一下英语，因此就凑合了一篇。不过本人英语不好，也懒得翻译，反正当时想自己看得懂就行了。今天心血来潮，突然觉得还蛮有用的，于是在这里现丑了，请大家指正。那位看得懂的帮忙翻译一下吧，我没空了。 <?php
/*
filename:SetGetTest.php
commentonassignmentbyvalueandreferrence
assuming$varisavarialbe,itshandle(pointer)isnamedas*var,
anditscontentisnamedas@var
thememoryareaof@varisreferredby*var,ifthe*varisthesame,
thenthememoryareasarethesame,so*varisjustlikeapointer.
1.when$var=$var1
var1,butinthedifferentmemoryarea,
new*varassignedbythesystem,pointingtothememoryareaholding@var
*varand*var1aredifferent
2.when$var=&$var1,
*varassignedby*var1,andthe@varisnotassignedorcopied,
itisabsolutelythesameas@var1,andinthesamememoryarea
both*varand*var1pointingtothememoryarea,thatmeanstheyarethesame.
passingbyreferrence
3.
functionset1(&$s){
$var=&$s;
}
set1($var1)results:
*var1passingtothefunction,and*sisthesameas*var1,
then*varisthesameas*s,theresultisthat*varisthesameas*var1
andallthecontentsarethesameobviously.
4.
functionset2(&$s){
$var=$s;
}
set2($var1)results:
*var1passingtothefunction,and*sisthesameas*var1,
butwhen$var=$sexecutes,from1.wecansees,
but*varisdifferentfrom*s,sosisnotinthesamememoryarea,
whilevar1issharingthesamememoryarea,also*var1and*sarethesame.
5.
normalfunctionreturn:
functionget(){return$var1;}
assumingtheresultisreferredbyavariable$result.
thenvar1but*resultisnotthesameas*var1
when$var=get();
firstyougetavariable$result,asIsaidabove,var1,but*result
isdifferentfrom*var1,andnext$var=$resultexecutes.
AsIsaidin1.,youcanfind,resultandthesameas@var1,
but*varisdifferentfrom*resultAND*var1;
while$var=&get()justmeans:
*varisthesameas*result,soresultareinthesamememoryarea,
buttheyarestilldifferentfromthoseof$var1,
boththememoryareaof@var1and*var1,
6.
returningbyreferrence
function&get(){return$var1;}
therearetwowaystogettheresult
$var=get();and$var=&get();nowIwilltellthedifference
I.$var=get();
the*resultisthesameas*var1andsovar1arethesame.
andthen$var=$resultexecutes,
*varisnotthesameas*result,andalsodifferentfrom*var1,
buttheircontentsarethesame.
I.$var=&get();
the*resultisthesameas*var1andsovar1arethesame.
andthen$var=&$resultexecutes,
thismeans$varand$resultarethesame,bothof@and*
*/
//thetestisthefollowing
functionprintln($s=""){
print"$s<br>";
}
classGetSetTest
{
var$var=null;
functionsetByRef(&$arg){
$this->var=&$arg;
}
functionpassByRef(&$arg){
$this->var=$arg;
}
functionsetByVal($arg){
$this->var=$arg;
}
function&getByRef(){
return$this->var;
}
functiongetByVal(){
return$this->var;
}
}
$o=newGetSetTest;
println("============setByRefgetByRef=============");
println("-----------------Beforechange----------------");
$in="beforechange";
$o->setByRef($in);
$outByVal=$o->getByRef();
$outByRef=&$o->getByRef();
println("$in:".$in);
println("$outByVal:".$outByVal);
println("$outByRef:".$outByRef);
println("$this->var:".$o->var);
println("-----------------Afterchange-----------------");
$in="afterchange";
println("$in:".$in);
println("$outByVal:".$outByVal);
println("$outByRef:".$outByRef);
println("$this->var:".$o->var);
println();
println("============setByRefgetByVal=============");
println("-----------------Beforechange----------------");
$in="beforechange";
$o->setByRef($in);
$outByVal=$o->getByVal();
$outByRef=&$o->getByVal();
println("$in:".$in);
println("$outByVal:".$outByVal);
println("$outByRef:".$outByRef);
println("$this->var:".$o->var);
println("-----------------Afterchange-----------------");
$in="afterchange";
println("$in:".$in);
println("$outByVal:".$outByVal);
println("$outByRef:".$outByRef);
println("$this->var:".$o->var);
println();
println("============passByRefgetByVal=============");
println("-----------------Beforechange----------------");
$in="beforechange";
$o->passByRef($in);
$outByVal=$o->getByVal();
$outByRef=&$o->getByVal();
println("$in:".$in);
println("$outByVal:".$outByVal);
println("$outByRef:".$outByRef);
println("$this->var:".$o->var);
println("-----------------Afterchange-----------------");
$in="afterchange";
println("$in:".$in);
println("$outByVal:".$outByVal);
println("$outByRef:".$outByRef);
println("$this->var:".$o->var);
println();
/*
以下输出结果是我（夜猫子）擅自编辑添加的，主要是为后来人查看方便加在这里，越肉代庖，向longnetpro致歉
输出结果：
============setByRefgetByRef=============
-----------------Beforechange----------------
$in:beforechange
$outByVal:beforechange
$outByRef:beforechange
$this->var:beforechange
-----------------Afterchange-----------------
$in:afterchange
$outByVal:beforechange
$outByRef:afterchange
$this->var:afterchange
============setByRefgetByVal=============
-----------------Beforechange----------------
$in:beforechange
$outByVal:beforechange
$outByRef:beforechange
$this->var:beforechange
-----------------Afterchange-----------------
$in:afterchange
$outByVal:beforechange
$outByRef:beforechange
$this->var:afterchange
============passByRefgetByVal=============
-----------------Beforechange----------------
$in:beforechange
$outByVal:beforechange
$outByRef:beforechange
$this->var:beforechange
-----------------Afterchange-----------------
$in:afterchange
$outByVal:beforechange
$outByRef:beforechange
$this->var:afterchange
*/
?>(责任编辑：admin) |
