speed: in_array versus long if($x=="x")||... list

biggus

I have a speed question. Does anyone know which is faster, in_array() or a long list of string comparisons in the if statement?

the if statement:

if( $extension=="avi"||
$extension=="asf"||
$extension=="doc"||
$extension=="dot"||
$extension=="exe"||
$extension=="gz"||
$extension=="jpeg"||
$extension=="jpg"||
$extension=="mp3"||
$extension=="mpeg"||
$extension=="mpg"||
$extension=="mov"||
$extension=="pdf"||
$extension=="pps"||
$extension=="ppt"||
$extension=="ram"||
$extension=="rar"||
$extension=="rm"||
$extension=="tar"||
$extension=="wav"||
$extension=="wma"||
$extension=="wmv"||
$extension=="xls"||
$extension=="zip"){...}

The array would have all of the above extensions. Is the if statement slower or is it close enough not to worry about?

Thanks,
Biggus

Kudose

Why don't you try it?

[MAN]microtime[/MAN]

biggus

I never tried that before, but have heard others doing it in some of the other langiagtes I use. I'll give it a shot.

Thanks.

liquorvicar

i wouldn't imagine there's much difference and the array method is much cleaner - easier to read and easier to update.

biggus

that's what I was thinking. The if statement just kept growing and growing. If I get around to it, I'll still try to time the code to see the difference.

Biggus

laserlight

If you're going to re-use the data, searching the array will probably be faster (since you only declare the array once), but for practical purposes the difference should be negligible since you probably wont be checking many times with the same data in a single script.

You could also consider using a switch-case structure with follow through, but in any case it is up to you to test and make the final decision.

biggus

the code is from a link-checker script I'm finishing. This part looks for specific file extensions and just check to make sure the file is there, otherwise the script sucks in the web page and check the links on it. So, a switch statement problably wouldn't do me any good. The array is more than likely ony going to be used in the one function, but I may make it a class variable anyway.

Thanks,
biggus

laserlight

So, a switch statement problably wouldn't do me any good.

Actually, you would use it like:

switch ($extension) {
case "avi":
case "asf":
case "doc":
case "dot":
case "exe":
case "gz":
case "jpeg":
case "jpg":
case "mp3":
case "mpeg":
case "mpg":
case "mov":
case "pdf":
case "pps":
case "ppt":
case "ram":
case "rar":
case "rm":
case "tar":
case "wav":
case "wma":
case "wmv":
case "xls":
case "zip":
	//extension found
	break;
default:
	//extension not found
}

biggus

that's true. I'm not accustomed to looking for more than one value per case in a switch statement, so I didn't think of it. They're supposed to be faster than if statements, IIRC. Thanks again.

Biggus