PHP Cookbook: Reversing a String by Word or Byte
You want to reverse the words or the bytes in a string.
Use strrev( ) to reverse by byte, as in Example 1-19.
Example 1-19. Reversing a string by byte
<?php print strrev('This is not a palindrome.'); ?>
Example 1-19 prints:
.emordnilap a ton si sihT
To reverse by words, explode the string by word boundary, reverse the words, and then rejoin, as in Example 1-20.
Example 1-20. Reversing a string by word
<?php $s = "Once upon a time there was a turtle."; // break the string up into words $words = explode(' ',$s); // reverse the array of words $words = array_reverse($words); // rebuild the string $s = implode(' ',$words); print $s; ?>
Example 1-20 prints:
turtle. a was there time a upon Once
Reversing a string by words can also be done all in one line with the code in Example 1-21.
Example 1-21. Concisely reversing a string by word
<?php $reversed_s = implode(' ',array_reverse(explode(' ',$s))); ?>
Recipe 23.7 discusses the implications of using something other than a space character as your word boundary; documentation on strrev( ) at http://www.php.net/strrev and array_reverse( ) at http://www.php.net/array-reverse.
Sumber: Adam Trachtenberg and David Sklar, PHP Cookbook, O’Reilly.