Need to generate numbers 1-1000000 in a list

<?php
 $lowestnum = 1;
 $highestnum = 1000000;
 
for($i=$lowestnum; $i<=$highestnum; $i++){
 echo "$i, ";
 }
 ?>

<?php
 $lowestnum = 1;
 $highestnum = 1000000;
 
for($i=$lowestnum; $i<=$highestnum; $i++){
 echo "$i<br />";
 }
 ?>

<?php
 $prefix = 'my prefix ';
 $lowestnum = 1;
 $highestnum = 1000000;
 
for($i=$lowestnum; $i<=$highestnum; $i++){
    echo "$prefix$i<br />";
}
?>

<?php echo "Hello World"; ?>

<?php 
 $prefix = 'my prefix ';
 $postfix = '<br />';
 $lowestnum = 1; 
 $highestnum = 1000000; 
  
for($i=$lowestnum; $i<=$highestnum; $i++){ 
    echo $prefix.$i.$postfix; 
} 
?>

http://php.net/echo