why is _ add in my foreach loop in php code example

Example 1: foreach loop in php

<?php
$arr = ['Item 1', 'Item 2', 'Item 3'];

foreach ($arr as $item) {
  var_dump($item);
}

$dict = array("key1"=>"35", "key2"=>"37", "key3"=>"43");

foreach($dict as $key => $val) {
  echo "$key = $val<br>";
}
?>

Example 2: php foreach

<?php
$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");

foreach($age as $x => $val) {
  echo "$x = $val<br>";
}
?>