php教程

count_chars

(PHP 4, PHP 5, PHP 7)

count_chars — 返回字符串所用字符的信息

说明

count_chars ( string $string [, int $mode = 0 ] ) : mixed

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。

参数

string

需要统计的字符串。

mode

参见返回的值。

返回值

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。

范例

Example #1 count_chars() 示例

<?php
$data = "Two Ts and one F.";

foreach (count_chars($data, 1) as $i => $val) {
   echo "There were $val instance(s) of \"" , chr($i) , "\" in the string.\n";
}
?>

以上例程会输出：

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

User Contributed Notes

Anonymous 26-Jan-2016 05:29
count_chars for multibyte supported.

<?php

function mb_count_chars ($string, $mode = 0) {
   
    $result =  array_fill(0, 256, 0);
   
    for ($i = 0, $size = mb_strlen($string); $i < $size; $i++) {
        $char = mb_substr($string, $i, 1);
        if (strlen($char) > 1) {
            continue;
        }
       
        $code = ord($char);
        if ($code >= 0 && $code <= 255) {
            $result[$code]++;
        }
    }
   
    switch ($mode) {
        case 1: // same as 0 but only byte-values with a frequency greater than zero are listed.
            foreach ($result as $key => $value) {
                if ($value == 0) {
                    unset($result[$key]);
                }
            }
            break;
        case 2: // same as 0 but only byte-values with a frequency equal to zero are listed.
            foreach ($result as $key => $value) {
                if ($value > 0) {
                    unset($result[$key]);
                }
            }
            break;
        case 3: // a string containing all unique characters is returned.
            $buildString = '';
            foreach ($result as $key => $value) {
                if ($value > 0) {
                    $buildString .= chr($key);
                }
            }
            return $buildString;
        case 4: // a string containing all not used characters is returned.
            $buildString = '';
            foreach ($result as $key => $value) {
                if ($value == 0) {
                    $buildString .= chr($key);
                }
            }
            return $buildString;
    }
   
    // change key names...
    foreach ($result as $key => $value) {
        $result[chr($key)] = $value;
        unset($result[$key]);
    }
   
    return $result;
   
}
?>
qeremy [atta] gmail [dotta] com 19-Jan-2013 06:06
Another approach to counting unicode chars.

<?php
function count_chars_unicode($str, $x = false) {
    $tmp = preg_split('//u', $str, -1, PREG_SPLIT_NO_EMPTY);
    foreach ($tmp as $c) {
        $chr[$c] = isset($chr[$c]) ? $chr[$c] + 1 : 1;
    }
    return is_bool($x)
        ? ($x ? $chr : count($chr))
        : $chr[$x];
}

$str = "?eker ?eker yariiiiiiiiiimmmmm";
print_r(count_chars_unicode($str, 'a'));    // frequency of "a"
print_r(count_chars_unicode($str));         // count of uniq chars
print_r(count_chars_unicode($str, true));   // all chars with own frequency
?>

Outputs;
1
9
Array
(
    [?] => 2
    [e] => 4
    [k] => 2
    [r] => 3
    [ ] => 2
    [y] => 1
    [a] => 1
    [i] => 10
    [m] => 5
)
marcus33cz 01-Feb-2012 11:43
If you have problems using count_chars with a multibyte string, you can change the page encoding. Alternatively, you can also use this mb_count_chars version of the function. Basically it is mode "1" of the original function.

<?php
/**
 * Counts character occurences in a multibyte string
 * @param string $input UTF-8 data
 * @return array associative array of characters.
 */
function mb_count_chars($input) {
    $l = mb_strlen($input, 'UTF-8');
    $unique = array();
    for($i = 0; $i < $l; $i++) {
        $char = mb_substr($input, $i, 1, 'UTF-8');
        if(!array_key_exists($char, $unique))
            $unique[$char] = 0;
        $unique[$char]++;
    }
    return $unique;
}

$input = "Let's try some Greek letters: αααααΕεΙιΜμΨψ, Russian: ЙЙЫЫЩН, Czech: ě????yáíé";
print_r( mb_count_chars($input) );
//returns: Array ( [L] => 1 [e] => 7 [t] => 4 ['] => 1 [s] => 5 [ ] => 9 [r] => 3 [y] => 1 [o] => 1 [m] => 1 [G] => 1 [k] => 1 [l] => 1 [:] => 3 [α] => 5 [Ε] => 1 [ε] => 1 [Ι] => 1 [ι] => 1 [Μ] => 1 [μ] => 1 [Ψ] => 1 [ψ] => 1 [,] => 2 [R] => 1 [u] => 1 [i] => 1 [a] => 1 [n] => 1 [Й] => 2 [Ы] => 2 [Щ] => 1 [Н] => 1 [C] => 1 [z] => 1 [c] => 1 [h] => 1 [ě] => 1 [?] => 1 [?] => 1 [?] => 1 [?] => 1 [y] => 1 [á] => 1 [í] => 1 [é] => 1 )
?>
phpC2007 04-Dec-2007 07:42
Here's a function to count number of strings in a string. It can be used as a simple utf8-enabled count_chars (but limited to a single mode)...

<?php
function utf8_count_strings($stringChar)
{
    $num = -1;
    $lenStringChar = strlen($stringChar);
   
    for ($lastPosition = 0;
        $lastPosition !== false;
        $lastPosition = strpos($textSnippet, $stringChar, $lastPosition + $lenStringChar))
    {
        $num++;
    }
   
    return $num;
}
?>
pzb at novell dot com 28-Jul-2007 06:29
This function is great for input validation.  I frequently need to check that all characters in a string are 7-bit ASCII (and not null).  This is the fastest function I have found yet:

<?php
function is7bit($string) {
    // empty strings are 7-bit clean
    if (!strlen($string)) {
        return true;
    }
    // count_chars returns the characters in ascending octet order
    $str = count_chars($str, 3);
    // Check for null character
    if (!ord($str[0])) {
        return false;
    }
    // Check for 8-bit character
    if (ord($str[strlen($str)-1]) & 128) {
        return false;
    }
    return true;
}
?>
apinpratap at gmail dot com 29-Mar-2007 10:54
this code can find each characters count

<?php
$enter = 0;
$data = strtolower ($inputString);
foreach (count_chars ($data, 1) as $i => $val)
    {
        if ($enter == 1)
        {
            $enter = 0;
            continue;
        }
        if (chr ($i) == "\n")
        {
            echo "There are $val instance(s) of \" Enter \" in the string.\n";
            $enter = 1;
        }
        else
        {
            echo "There are $val instance(s) of \"" , chr ($i) , "\" in the string.\n";
        }
    }
?>
Eric Pecoraro 27-May-2005 07:31
<?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';
    }
}

?>
seb at synchrocide dot net 16-May-2004 03:08
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 29-Jan-2002 04:27
// 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 31-Jan-2001 05:04
Here are some more experiments on this relatively new and extremely handy function.

<?php
$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). 

<?php
$length_of_string = strlen($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?)

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