Cannot reproduce.
sem_release() DOES remove the semaphor if no other process uses it.

I think it doesn't.
In my script I have class Semaphore.
There are methods like acquire() and release().
After each sem_acquire instruction I wrote:

echo('I\'ve  acquired semaphore key: ' . $this->key . '<br>');

After each  sem_release instruction I wrote:

echo('I\'ve released semaphore key: ' . $this->key . '<br>');

I have executed script only once.
The result I saw is:

I've acquired semaphore key: 1376159737
I've released semaphore key: 1376159737
I've acquired semaphore key: 1376159747
I've released semaphore key: 1376159747
I've acquired semaphore key: 1376159737
I've released semaphore key: 1376159737
I've acquired semaphore key: 1376159748
I've released semaphore key: 1376159748
I've acquired semaphore key: 1376159737
I've released semaphore key: 1376159737
I've acquired semaphore key: 1376159749
I've released semaphore key: 1376159749

As you can see each semaphore is released.
But when I run command ipcs -s on my server I get:

------ Semaphore Arrays --------
key        semid      owner      perms      nsems     
0x520687e6 131075     www_php-a 600        3         
0x520687f9 163844     www_php-a 600        3         
0x520687fa 196613     www_php-a 600        3         
0x520687fc 229382     www_php-a 600        3         
0x520687e9 262151     www_php-a 600        3         
0x520687fd 294920     www_php-a 600        3         
0x520687fe 327689     www_php-a 600        3         
0x520687ff 360458     www_php-a 600        3         
0x52068800 393227     www_php-a 600        3         
0x52068801 425996     www_php-a 600        3         
0x52068802 458765     www_php-a 600        3         
0x52068803 491534     www_php-a 600        3         
0x52068804 524303     www_php-a 600        3         
0x52068805 557072     www_php-a 600        3         

You can see that there are not removed semaphores.

Next code.

I have a test script with code as follows:

<?php
$id = sem_get(10);
sem_acquire($id);
for($ind = 0; $ind < 10000; $ind++) { }
sem_release($id);
?>

I run it only once.

The result I get after execute command ipcs -s on the server:

------ Semaphore Arrays --------
key        semid      owner      perms      nsems     
0x0000000a 131075     www_php-a 666        3         

It seems that there is a problem with semaphores' removal after release.

I think that there is also a problem with parameter max_acquire because value in column nsems always equals 3

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

if you want to remove the semaphore you need to call the 
sem_remove() function. Closing the semaphore won't remove it 
no more so then closing a file will remove it from disk.

I think you don't understand me.
I know that sem_release doesn't remove the semaphore but I think it should because it's the one and only way to do it correct, of course if current process, which releases a semaphore, is the last one which acquired it.

Please, read one more time bug's description.
I think you didn't understand my intention.

I'm changing the status to Open

I will try to tell about my sugestion.

I assume that I have a function my_sem_remove($sem_id):

function my_sem_remove($id) {
  if(Semaphore $id isn't acquired and its FIFO is empty)
    sem_remove($id);
}
None of instructions in this function can be interrupted.
So, now the problem is simple to resolve:

$id = sem_get(ID);
sem_acquire($id);

CRITICAL REGION

sem_release($id);
my_sem_remove($id);

But now, two instructions: sem_release and my_sem_remove are not needed. It's simple to replace them by one function my_sem_release:

function my_sem_release($id) {
  sem_release($id);
  my_sem_remove($id);
}

For reasons which about I will write later those instructions can't be interrupted.

So, my example look like this:

$id = sem_get(ID);
sem_acquire($id);

CRITICAL REGION

my_sem_release($id);

But let's imagine two concurrent processes executing code above:

PROC1: $id = sem_get(ID);
<---  interrupt
PROC2: $id = sem_get(ID);
       sem_acquire($id);
       CRITICAL REGION
       my_sem_release($id);
<--- interrupt
PROC1: sem_acquire($id); <--- Uuups!! Error: semaphore doesn't exists, PROC2 has removed it.

My solution:
Instructions sem_get and sem_acquire can't be interrupted.
So, I assume that there is a function my_sem_acquire:

function my_sem_acquire($key, $max_acquire = 1, $perm = 0666, $auto_release = true) {

  $id = sem_get($key, $max_acquire, $perm, $auto_release);
  sem_acquire();
  return $id;
}

None of instructions in function above can be interrupted.

And finally correct example:

$id = my_sem_acquire(SEMKEY);

CRITICAL REGION

my_sem_release($id);

It's the best solutions without danger of operating on not existing semaphores. Also, unused semaphores are automaticcally removed. The problem is, that functions my_sem_acquire and my_sem_release can't be witten in PHP so it must be done in C inside source of PHP.

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

If you want, please make a feature request. However, the 
current behavior is absolutely correct.