# 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

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