<?php

function gen() {
  $a = array('a' => 'apple', 'b' => 'banana', 'c' => 'citrus');
  foreach ($a as $k1 => &$v1) {
    foreach ($a as $k2 => &$v2) {
      if ($k2 == 'a') {
        unset($a[$k2]);
      }
      var_dump($v1, $v2);
    }
  }
  yield null;
}
foreach (gen() as $_) {
}