Rotate a string N times in PHP

Question

I'm looking for a way to rotate a string to the left N times. Here are some examples:

Let the string be abcdef

• if I rotate it 1 time I want bcdefa
• if I rotate it 2 time I want cdefab
• if I rotate it 3 time I want defabc
• .
• .
• If I rotate the string its string length times, I should get back the original string.

Answer 1

function rotate_string ($str, $n)
{
    while ($n > 0)
    {
        $str = substr($str, 1) . substr($str, 0, 1);
        $n--;
    }

    return $str;
}

Answer 2

There is no standard function for this but is easily implemented.

function rotate_left($s) {
  return substr($s, 1) . $s[0];
}

function rotate_right($s) {
  return substr($s, -1) . substr($s, 0, -1);
}

You could extend this to add an optional parameter for the number of characters to rotate.

Answer 3

 $rotated = substr($str, $n) . substr($str, 0, $n);

Answer 4

Here is one variant that allows arbitrary shifting to the left and right, regardless of the length of the input string:

function str_shift($str, $len) {
    $len = $len % strlen($str);
    return substr($str, $len) . substr($str, 0, $len);
}

echo str_shift('abcdef', -2);  // efabcd
echo str_shift('abcdef', 2);   // cdefab
echo str_shift('abcdef', 11);  // fabcde

Answer 5

Use this code

<?php
    $str = "helloworld" ;
    $res = string_function($str,3) ;
    print_r ( $res) ;
    function string_function ( $str , $count )
    {
    $arr = str_split ( $str );
    for ( $i=0; $i<$count ; $i++ )
    {
      $element = array_pop ( $arr ) ;
      array_unshift ( $arr, $element ) ;
    }
    $result=( implode ( "",$arr )) ;
    return $result;
    }
    ?>