How to check if two strings are anagrams in PHP?

PHP: How to check if two strings are anagrams in PHP?

This is a classic simple programming question. There are several ways to approach this problem. Here is one solution:

The comparison function:

  1. function is_anagram($a, $b)
  2. {
  3.  
  4.     if (strlen($a) != strlen($b)) {
  5.         // if not same size then they definitely aren't
  6.         return false;
  7.     }
  8.  
  9. // turn 'foobar' into ['f', 'o', 'o', 'b', 'a', 'r']
  10. $a_chars = str_split($a);
  11. $b_chars = str_split($b);
  12.  
  13. // sort them...
  14. sort($a_chars);
  15. sort($b_chars);
  16.  
  17. // check if they're exactly the same...
  18. return $a_chars === $b_chars;
  19.  
  20. // another way to do this that someone emailed me about, which is much more simple:
  21. // return (count_chars($a, 1) == count_chars($b, 1))
  22.  
  23.  
  24. }

Let's write some tests

  1. $anagrams = [
  2.  
  3.     // $a, $b, $is_valid_anagram
  4.  
  5.         ["asdf", "asdf", true],
  6.         ["asdf", "fdsa", true],
  7.         ["asdfasdf", "asdfasdf", true],
  8.         ["a", "a", true],
  9.         ["a", "b", false],
  10.         ["aaa", "aaa", true],
  11.         ["aaa", "aa", false],
  12.         ["aaaa", "abab", false],
  13.         ["qwerty", "asdfg", false]
  14.  
  15. ];

And now let's go through each one.

  1. foreach ($anagrams as $anagram) {
  2.  
  3.     [$a, $b, $is_valid_anagram] = $anagram;
  4.  
  5.     $result = is_anagram($a, $b);
  6.     $result_message = $result ? "Is an anagram" : "Is not an anagram";
  7.  
  8.     if ($result != $is_valid_anagram) {
  9.         throw new \Exception("The anagram function returned an incorrect result for $a and $b");  // this doesn't happen with our function! :)
  10.     }
  11.     var_dump("[$a] and [$b] $result_message");
  12.  
  13. }

"Our function said that [asdf] and [asdf] Is an anagram, which is correct"
"Our function said that [asdf] and [fdsa] Is an anagram, which is correct"
"Our function said that [asdfasdf] and [asdfasdf] Is an anagram, which is correct"
"Our function said that [a] and [a] Is an anagram, which is correct"
"Our function said that [a] and [b] Is not an anagram, which is correct"
"Our function said that [aaa] and [aaa] Is an anagram, which is correct"
"Our function said that [aaa] and [aa] Is not an anagram, which is correct"
"Our function said that [aaaa] and [abab] Is not an anagram, which is correct"
"Our function said that [qwerty] and [asdfg] Is not an anagram, which is correct"

BTW, not sure about how the [$a, $b, $is_valid_anagram] = $anagram; line works? See my blog post about array destructuring in PHP 7.

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webdevetc

I am a 29 year old backend web developer from London, mostly focusing on PHP and Laravel lately. This (webdevetc.com) is my blog where I write about some web development topics (PHP, Laravel, Javascript, and some server stuff). contact me here.



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