iterate through array, number of keys is variable, the first value being processed differently

$first = array_shift($array);
// do something with $first

foreach ($array as $key => $value) {
    // do something with $key and $value
}

I would do this:

$firstDone = FALSE;
foreach ($array as $value) {
  if (!$firstDone) {
    // Process first value here
    $firstDone = TRUE;
  } else {
    // Process other values here
  }
}

...but whether that is the best way is debatable. I would use foreach over any other method, because then it does not matter what the keys are.

Here is one way:

$first = true;
foreach($array as $key => $value) {
    if ($first) {
        // something different
        $first = false;
    }
    else {
        // regular logic
    }
}

   $i = 0;
   foreach($ur_array as $key => $val) {
      if($i == 0) {
         //first index

      }
      else {
         //do something else
      }

      $i++;
   }

I would do it like this if you're sure the array contains at least one entry:

processFirst($myArray[0]);

for ($i=1; $i<count($myArray); $1++)
{
    processRest($myArray[$i]);
}

Otherwise you'll need to test this before processing the first element

I've made you a function!

function arrayCallback(&$array) {
    $callbacks = func_get_args(); // get all arguments
    array_shift($callbacks); // remove first element, we only want the callbacks

    $callbackindex = 0;

    foreach($array as $value) {
        // call callback
        $callbacks[$callbackindex]($value);

        // make sure it keeps using last callback in case the array is bigger than the amount of callbacks
        if(count($callbacks) > $callbackindex + 1) {
            $callbackindex++;
        }
    }
}

If you call this function, it accepts an array and infinite callback arguments. When the array is bigger than the amount of supplied functions, it stays at the last function.

You can simply call it like this:

arrayCallback($array, function($value) {
    print 'callback one: ' . $value;
}, function($value) {
    print 'callback two: ' . $value;
});

EDIT

If you wish to avoid using a function like this, feel free to pick any of the other correct answers. It's just what you prefer really. If you're repeatedly are planning to loop through one or multiple arrays with different callbacks I suggest to use a function to re-use code. (I'm an optimisation freak)