How PHP programming improves program running efficiency

From this we can see that the second part of the code will constantly judge the number of keys in the array to 1 2 3, so it turns into the first part of the code is 3, the second part of the code is judged six times.

I 've been switching from. NET to PHP4 for years and recently started to pursue high performance ~~
So I thought it was time to write a blog ~
Come to discover things first ~
<? Php
$ Arr = array (
Attr1 => 1,
Attr2 => 1,
Attr3 => 1,
);
$ StartTime = microtime (true );
For ($ I = 0; I I <1000; $ I)
{
If (isset ($ arr [attr1])
{
}
If (isset ($ arr [attr2])
{
}
If (isset ($ arr [attr3])
{
}
}
$ EndTime = microtime (true );
Printf ("% d us.", ($ endTime-$ startTime) * 1000000 );
$ StartTime = microtime (true );
For ($ I = 0; I I <1000; $ I)
{
Foreach ($ arr as $ key => $ value)
{
Switch ($ key)
{
Case attr1:
Break;
Case attr2:
Break;
Case attr3:
Break;
}
}
}
$ EndTime = microtime (true );
Printf ("% d us.", ($ endTime-$ startTime) * 1000000 );
?>
The above code
The output result is
Us.
Us.
However, the first section is more complex than the second section, and the structure is not clear in the second section,
So why is the first segment much faster than the second segment?
We can see that the first code contains only three if,
So how many will there be in the second segment.
Let's take a look at the basic implementation principle of switch.
If break is used in each case in the switch,
In fact, this switch is like multiple if {} else if {}

So from this mechanism, we can
<? Php
Foreach ($ arr as $ key => $ value)
{
Switch ($ key)
{
Case attr1:
Break;
Case attr2:
Break;
Case attr3:
Break;
}
}
?>
Convert
<? Php
Foreach ($ arr as $ key => $ value)
{
If ($ key = attr1)
{

}
Else if ($ key = attr2)
{

}
Else if ($ key = attr3)
{

}
}
?>
To understand this, we can see that the second part of the code will constantly judge the number of keys in the array based on the number of keys, therefore, the first code Judge 3 times, and the second code judge 6 times.