count_chars

(PHP 4, PHP 5, PHP 7, PHP 8)

count_chars — 返回字符串所用字符的信息

说明

count_chars(string $string, int $mode = 0): array|string

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。

更新日志

版本	说明
8.0.0	在此版本之前，函数在失败时返回 `false`。

示例

示例 #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";
}
?>

以上示例会输出：

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

strpos() - 查找字符串首次出现的位置
substr_count() - 计算字串出现的次数

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用户贡献的备注 8 notes

down

marcus33cz ¶

12 years ago

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;
}

$input = "Let's try some Greek letters: αααααΕεΙιΜμΨψ, Russian: ЙЙЫЫЩН, Czech: ěščřžýáíé";
print_r( mb_count_chars($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 [š] => 1 [č] => 1 [ř] => 1 [ž] => 1 [ý] => 1 [á] => 1 [í] => 1 [é] => 1 )
?>

down

Eric Pecoraro ¶

19 years ago

<?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';
    }
}

?>

down

seb at synchrocide dot net ¶

20 years ago

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

down

Anonymous ¶

8 years ago

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;
    
}
?>

down

-1

Andrey G ¶

4 years ago

Checking that two strings are anagram:

<?php

function isAnagram($string1, $string2)
{
  return count_chars($string1, 1) === count_chars($string2, 1);
}

isAnagram('act', 'cat'); // true

?>

down

-1

pzb at novell dot com ¶

17 years ago

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;
}
?>

down

-3

phpC2007 ¶

16 years ago

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;
}
?>

down

-5

mlong at mlong dot org ¶

22 years ago

// 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")];

?>