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# count_chars

(PHP 4, PHP 5)

count_chars -- 返回字符串所用字符的信息

## 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()。

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