How to implement string flip function in PHP

When it comes to the method of achieving string reversal, everyone will think of using a loop. Indeed, looping is a small memory footprint and simple to implement. But there is another way to achieve such a function, and that is recursion.

PHP supports recursive functions, which are functions that call themselves. These functions are particularly useful for dynamically browsing data structures such as joined lists and trees.

Example:

<?php 
//递归实现字符串翻转
function reverse_r($str){
  if(strlen($str)>0){
    reverse_r(substr($str,1));
  }
  echo substr($str,0,1);
  return;
}
//循环实现字符串翻转
function reverse_i($str){
  for($i=1; $i<=strlen($str);$i++){
    echo substr($str,-$i,1);
  }
  return;
}
reverse_r("Hello");
reverse_i("everyone");
?>

result:

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How to implement string flip in PHP

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