由php中字符offset特征造成的繞過漏洞詳解
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2023-12-08
(PHP 4, PHP 5)
count_chars — 返回字符串所用字符的信息
說明
mixed count_chars ( string$string
[, int $mode = 0
] )
統計 string
中每個字節值（0..255）出現的次數，使用多種模式返回結果。
參數
string
需要統計的字符串。
mode
參見返回的值。
返回值
根據不同的 mode，count_chars()
返回下列不同的結果：
0 - 以所有的每個字節值作為鍵名，出現次數作為值的數組。
1 - 與 0 相同，但只列出出現次數大于零的字節值。
2 - 與 0 相同，但只列出出現次數等于零的字節值。
3 - 返回由所有使用了的字節值組成的字符串。
4 - 返回由所有未使用的字節值組成的字符串。
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";
}
?>
以上例程會輸出：
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.
參見
strpos() - 查找字符串首次出現的位置 substr_count() - 計算字串出現的次數
