PHP recursive function small example

function reversr_r($str)
{
if (strlen($str)>0)
reverse_r(substr($str,1));
echo substr($str,0 ,1);
return;
}
?>

function reverse_i($str)
{
for($i=1;$i<=strlen($str);$i++)
{
echo substr($str,-$i,1);
}
}

Code analysis: Implement two functions, both of which can print the contents of a string in reverse order. The function reversr_r is implemented through recursion, while the function reverse_i() is implemented through looping.