count_chars

描述

mixed count_chars ( string string [, int mode] )

统计 string 中每个字节值（0..255）出现的次数，使用多种模式返回结果。可选参数 mode 默认值为 0。根据不同的 mode，count_chars() 返回下列不同的结果：

0 - 以所有的每个字节值作为键名，出现次数作为值的数组。
1 - 与 0 相同，但只列出出现次数大于零的字节值。
2 - 与 0 相同，但只列出出现次数等于零的字节值。
3 - 返回由所有使用了的字节值组成的字符串。
4 - 返回由所有未使用的字节值组成的字符串。

例子 1. count_chars() 示例
<?php $data = "Two Ts and one F."; $result = count_chars($data, 0); for ($i=0; $i < count($result); $i++) { if ($result[$i] != 0) echo "There were $result[$i] instance(s) of \"" , chr($i) , "\" in the string.\n"; } ?>
下边为示例输出：
There were 4 instance(s) of " " in the string. There were 1 instance(s) of "." in the string. There were 1 instance(s) of "F" in the string. There were 2 instance(s) of "T" in the string. There were 1 instance(s) of "a" in the string. There were 1 instance(s) of "d" in the string. There were 1 instance(s) of "e" in the string. There were 2 instance(s) of "n" in the string. There were 2 instance(s) of "o" in the string. There were 1 instance(s) of "s" in the string. There were 1 instance(s) of "w" in the string.

参见 strpos() 和 substr_count()。

add a note User Contributed Notes

Eric Pecoraro
27-May-2005 10:31


<?php



// Require (n) unique characters in a string

// Modification of a function below which ads some flexibility in how many unique characters are required in a given string.



$pass = '123456' ; // true

$pass = '111222' ; // false



req_unique($pass,3);



function req_unique($string,$unique=3) {

    if ( count(count_chars($string,1)) < $unique) {

        echo 'false';

    }else{

        echo 'true';

    }

}



?>

Alex Gemmell
15-Feb-2005 02:03


Use: Great for checking for unique characters in a password.



I wanted to check that my website users, when registering a user account, chose a "valid" (not-so-easily-guessed) password.



One of the many checks was that the password must have 6 unique characters.  I was tying myself in knots with all kinds of recursive array calling when I was offered this wonderful one line solution:



function check_password($password) {



   #Have 6 unique characters

   if (count(count_chars($password, 1)) < 6) return false;



   #

   # other checks returning false as necessary

   #

   #



   return true;

}



I cannot claim this wonderful line for myself - a Mr Lynch suggested this to me.  Thanks!

seb at synchrocide dot net
17-May-2004 06:08


After much trial and error trying to create a function that finds the number of unique characters in a string I same across count_chars() - my 20+ lines of useless code were wiped for this:



<?

function unichar($string) {

$two= strtolower(str_replace(' ', '', $string));

$res = count(count_chars($two, 1));

return $res;

}



/* examples :: */



echo unichar("bob"); // 2

echo unichar("Invisibility"); //8

echo unichar("The quick brown fox slyly jumped over the lazy dog"); //26



?>



I have no idea where this could be used, but it's quite fun

mlong at mlong dot org
30-Jan-2002 08:27


// Usefulness of the two functions





<?php


 $string="aaabbc";





 // You just want to count the letter a


 $acount=substr_count($string,"a");





 // You want to count both letter a and letter b


 $counts=count_chars($string,0);


 $acount=$counts[ord("a")];


 $bcount=$counts[ord("b")];


?>

maotin at hongkong dot com
01-Feb-2001 09:04


Here are some more experiments on this relatively new and extremely handy function.





$string = 'I have never seen ANYTHING like that before! My number is "4670-9394".';





foreach(count_chars($string, 1) as $chr => $hit)


echo 'The character '.chr(34).chr($chr).chr(34).' has appeared in this string '.$hit.' times.<BR>';





#The result looks like


#The character " " has appeared in this string 11 times.





echo count_chars($string,3);


#The output is '!"-.034679AGHIMNTYabefhiklmnorstuvy'





echo strlen($string).' is not the same as '.strlen(count_chars($string, 3));





#This shows that '70 is not the same as 36'





As we can see above:





1)If you cares only about what is in the string, use count_chars($string, 1) and it will return an (associative?) array of what shows up only.





2) Either I misunderstood what the manul actually said, or it does not work the way it described: count_chars($strting, 3) actually returned a string of what characters are in the string, not a string of their byte-values (which is great because a string of numbers would be much harder to handle);





3)This is a short version of password checking: get the original string's length, then compare with the length of the string returned by count_chars($string,3).  





$length_of_string = strlen($string);


$num_of_chars = strlen(count_chars($string, 3));





$diff = ($length_of_string - $num_of_chars);





if ($diff)


echo 'At least one character has been used more than once.';


else


echo 'All character have been used only once.;





Note that since $num_of_chars gives no information about the actual number of occurance, we cannot go any further by the same rationale and say when $diff =2 then 2 characters showed up twice; it might be 1 character showd up 3 times, we have no way to tell (a good tolerance level setter, though).  You have to get the array and check the values if you want to have more control.





4) Final trick: now we have a primitive way to count the number of words in a string! (or do we have a fuction for that already?)

add a note