SOX LAME and php fire done signal?

Hi I am using SOX in the following manner with php:

$thesong = 67;

$theString = "1.wav 2.wav 2.wav 1.wav";

exec("./sox $theString $thesong.wav");

It seems to be be working very good, Then I do the following:

exec("./lame $thesong.wav $thesong.mp3");

Again this works fine, but is there any way to开发者_开发问答 tell when both SOX and LAME have completed the encoding?

I mean do they send out a "I Am Done" signal?

Something like:

if(soxdone && lamedone)
{
  //further processing?
}

Try Something like this:

if(exec("./lame $thesong.wav $thesong.mp3") && exec("./sox $theString $thesong.wav"))
{
   //further processing 
}