I want to find how many unique characters a string contains. Examples:
"66615888" contains 4 digits (6 1 5 8).
"12333333345" contains 5 digits (1 2 3 4 5).
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Do you care about the order in which the numbers (characters) are returned?Floris– Floris2013-03-13 16:47:39 +00:00Commented Mar 13, 2013 at 16:47
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Question as asked is asking for "how many" unique characters, rather than a list of them.merlin2011– merlin20112013-03-13 17:01:55 +00:00Commented Mar 13, 2013 at 17:01
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@Floris I don't, only need "how many".jlee– jlee2013-03-13 17:06:42 +00:00Commented Mar 13, 2013 at 17:06
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5 Answers
echo count( array_unique( str_split( '66615888')));
Docs:
count()- Count the number of elements in an arrayarray_unique()- Find the unique elements in an arraystr_split()- Split a string into an array
4 Comments
insertusernamehere
+1 But let me ask: Do you know which performs better: your solution or merlin2011's/NikiC's?
jlee
@insertusernamehere I dont know. which one is better?
nickb
@insertusernamehere - A simple test tells me NikiC's is faster after 1,000,000 iterations. I prefer this way as IMO it is more readable.
insertusernamehere
Thanks for testing. I thought that creating the array will produce some overhead and a direct string manipulation might be faster. But if this runs only a few times, in the end it's only micro optimization.
count_chars gives you a map of char => frequency, which you can sum up with with array_sum:
$count = array_sum(count_chars($str));
Alternatively you can use the 3 mode for count_chars which will give you a string containing all unique characters:
$count = strlen(count_chars($str, 3));
1 Comment
Floris
I prefer this answer over the "accepted" one. Creating an array of all the elements is a lot of overhead -
count_chars(,3) is the most direct way to get all the unique characters, and the strlen of that is the count - which is what was asked. It gets my vote.PHP has a function that counts characters.
$data = "foobar";
$uniqued = count_chars($data, 3);// return string(5) "abfor"
$count = strlen($uniqued);
Please see the documentation here.
Comments
You can use the following script:
<?php
$str1='66615888';
$str2='12333333345';
echo 'The number of unique characters in "'.$str1.'" is: '.strlen(count_chars($str1,3)).' ('.count_chars($str1,3).')'.'<br><br>';
echo 'The number of unique characters in "'.$str2.'" is: '.strlen(count_chars($str2,3)).' ('.count_chars($str2,3).')'.'<br><br>';
?>
Output:
The number of unique characters in "66615888" is: 4 (1568)
The number of unique characters in "12333333345" is: 5 (12345)
Here PHP string function count_chars() in mode 3 produces an array having all the unique characters.
PHP string function strlen() produces total number of unique characters present.
Comments
Here is another version that also works with multibyte strings:
echo count(array_keys(array_flip(preg_split('//u', $str, null, PREG_SPLIT_NO_EMPTY))));
