在VB中，我们经常要处理字符串列表，为图方便，有人喜欢用Collection来寄存字串列表，引用时再使用Collection.Item(Index)读取。Collection确实很方便，但Collection的读取效率极低，需要频繁调用的数据最好不要用Collection寄存，改用数组，效果会好几亿倍。不信你自己测试一下
测试代码：
Private Sub Form_Load()
Dim t As Double, i As Long, t1 As Double, t2 As Double
t = Timer
For i = 1 To 10000
col.Add "StringTest"
Next
t1 = Timer - t
t = Timer
For i = 1 To 10000
ReDim Preserve SA(i - 1)
SA(i - 1) = "StringTest"
Next
t2 = Timer - t
Debug.Print "Load", t1, t2, t1 / t2
End Sub
Private Sub引用_Click()
Dim i As Long, s As String
Dim t As Double, t1 As Double, t2 As Double
t = Timer
For i = 1 To col.Count
s = col.Item(i)
Next
t1 = Timer - t
t = Timer
For i = LBound(SA) To UBound(SA)
s = SA(i)
Next
t2 = Timer - t
Debug.Print "引用", t1, t2, t1 / t2
End Sub
Private Sub Load2_Click()
Dim t As Double, i As Long, t1 As Double, t2 As Double
Set col = Nothing
t = Timer
For i = 1 To 10000
col.Add "StringTest"
Next
t1 = Timer - t
t = Timer
ReDim SA(10000 - 1)
For i = 1 To 10000
SA(i - 1) = "StringTest"
Next
t2 = Timer - t
Debug.Print "Load2", t1, t2, t1 / t2
End Sub
下图是我的测试结果：
看看第三行第三个数据就知道差别了！！！
/*
图片验证码 Powered By KASON
转载请注明出处:http://www.cnblogs.com/kason/
*/
session_start();
$num=4;//验证码个数
$width=80;//验证码宽度
$height=20;//验证码高度
$code=' ';
for($i=0;$i<$num;$i++)//生成验证码
{
switch(rand(0,2))
{
case 0:$code[$i]=chr(rand(48,57));break;//数字
case 1:$code[$i]=chr(rand(65,90));break;//大写字母
case 2:$code[$i]=chr(rand(97,122));break;//小写字母
}
}
$_SESSION["VerifyCode"]=$code;
$image=imagecreate($width,$height);
imagecolorallocate($image,255,255,255);
for($i=0;$i<80;$i++)//生成干扰像素
{
$dis_color=imagecolorallocate($image,rand(0,2555),rand(0,255),rand(0,255));
imagesetpixel($image,rand(1,$width),rand(1,$height),$dis_color);
}
for($i=0;$i<$num;$i++)//打印字符到图像
{
$char_color=imagecolorallocate($image,rand(0,2555),rand(0,255),rand(0,255));
imagechar($image,60,($width/$num)*$i,rand(0,5),$code[$i],$char_color);
}
header("Content-type:image/png");
imagepng($image);//输出图像到浏览器
imagedestroy($image);//释放资源