不确定是否还有必要。但是下面的解决方案应该与迭代器一起工作，并且不需要计数。

<?php

foreach_first_last(array(), function ($key, $value, $step, $first, $last) {
    echo intval($first), ' ', intval($last), ' ', $step, ' ', $value, PHP_EOL;
});

foreach_first_last(array('aa'), function ($key, $value, $step, $first, $last) {
    echo intval($first), ' ', intval($last), ' ', $step, ' ', $value, PHP_EOL;
});
echo PHP_EOL;

foreach_first_last(array('aa', 'bb', 'cc'), function ($key, $value, $step, $first, $last) {
    echo intval($first), ' ', intval($last), ' ', $step, ' ', $value, PHP_EOL;
});
echo PHP_EOL;

function foreach_first_last($array, $cb)
{
    $next = false;
    $current = false;
    reset($array);
    for ($step = 0; true; ++$step) {
        $current = $next;
        $next = each($array);
        $last = ($next === false || $next === null);
        if ($step > 0) {
            $first = $step == 1;
            list ($key, $value) = $current;
            if (call_user_func($cb, $key, $value, $step, $first, $last) === false) {
                break;
            }
        }
        if ($last) {
            break;
        }
    }
}

对于键和值，这也是有效的:

foreach ($array as $key => $value) {
    if ($value === end($array)) {
        echo "LAST ELEMENT!";
    }
}

可以使用计数器和数组长度。

    $array = array(1,2,3,4);

    $i = 0;
    $len = count($array);
    foreach ($array as $item) {
        if ($i === 0) {
            // first
        } else if ($i === $len - 1) {
            // last
        }
        // …
        $i++;
    }

这很简单!

// Set the array pointer to the last key
end($array);
// Store the last key
$lastkey = key($array);  
foreach($array as $key => $element) {
    ....do array stuff
    if ($lastkey === key($array))
        echo 'THE LAST ELEMENT! '.$array[$lastkey];
}

谢谢你@billynoah整理了最后的问题。

最简单的方法是

$array = [9,5,6,4,7,8];

$current_iteration = 0;

foreach($array as $item){
  if( 0 === $current_iteration ){
    echo 'this is the first item: ' . $item;
  }

  if( (count($array) - 1) === $current_iteration){
    echo 'this is the last item: ' . $item;
  }

  $current_iteration++;
}

上面的一个更简化的版本，并假设您不使用自定义索引……

$len = count($array);
foreach ($array as $index => $item) {
    if ($index == 0) {
        // first
    } else if ($index == $len - 1) {
        // last
    }
}

版本2 -因为我已经讨厌使用else除非必要。

$len = count($array);
foreach ($array as $index => $item) {
    if ($index == 0) {
        // first
        // do something
        continue;
    }

    if ($index == $len - 1) {
        // last
        // do something
        continue;
    }
}