运行以下代码：

$tag = 互联网产品、码探秘; $text = rtrim($tag,乱码 "、"); print_r($text);

运行，码探秘我们可能以为会得到的乱码结果是 互联网产品 ，实际结果是码探秘 互联网产� 。为什么会这样呢？乱码

原理

trim 函数文档

string trim ( string $str [, string $character_mask = " \t\n\r\0\x0B" ] )

该函数不是多字节函数，也就是码探秘说，汉字这样的乱码多字节字符，会拿其头或尾的云服务器码探秘单字节来和后面的 $character_mask 对应的char数组进行匹配，如果在后面的乱码数组中，则删掉，码探秘继续匹配。乱码比如：

echo ltrim("bcdf",码探秘"abc"); // df

如下面的 demo 中的函数 string_print_char 所示：

、 由 0xe3 0x80 0x81 三字节组成，乱码

品 由 0xe5 0x93 0x81 三字节组成。码探秘

所以在执行 rtrim 的时候，云服务器提供商通过字节比对，会将 0x81 去掉，导致了***出现了乱码。

源码精简版演示

查看 PHP7 的源码，然后提炼出下面的小 demo ，方便大家一起学习，其实PHP源码的学习并不难，每天进步一点点。

// // main.c // trim // // Created by 周梦康 on 2017/10/18. // Copyright © 2017年 周梦康. All rights reserved. // #include <stdio.h> #include <stdlib.h> #include <string.h> void string_print_char(char *str); void php_charmask(unsigned char *input, size_t len, char *mask); char *ltrim(char *str,char *character_mask); char *rtrim(char *str,char *character_mask); int main(int argc, char const *argv[]) { printf("%s\n",ltrim("bcdf","abc")); string_print_char("品"); // e5 93 81 string_print_char("、"); // e3 80 81 printf("%s\n",rtrim("互联网产品、","、亿华云")); return 0; } char *ltrim(char *str,char *character_mask) { char *res; char mask[256]; register size_t i; int trimmed = 0; size_t len = strlen(str); php_charmask((unsigned char*)character_mask, strlen(character_mask), mask); for (i = 0; i < len; i++) { if (mask[(unsigned char)str[i]]) { trimmed++; } else { break; } } len -= trimmed; str += trimmed; res = (char *) malloc(sizeof(char) * (len+1)); memcpy(res,str,len); return res; } char *rtrim(char *str,char *character_mask) { char *res; char mask[256]; register size_t i; size_t len = strlen(str); php_charmask((unsigned char*)character_mask, strlen(character_mask), mask); if (len > 0) { i = len - 1; do { if (mask[(unsigned char)str[i]]) { len--; } else { break; } } while (i-- != 0); } res = (char *) malloc(sizeof(char) * (len+1)); memcpy(res,str,len); return res; } void string_print_char(char *str) { unsigned long l = strlen(str); for (int i=0; i < l; i++) { printf("%02hhx\t",str[i]); } printf("\n"); } void php_charmask(unsigned char *input, size_t len, char *mask) { unsigned char *end; unsigned char c; memset(mask, 0, 256); for (end = input+len; input < end; input++) { c = *input; mask[c]= 1; } }

PHP7 相关源码

PHP_FUNCTION(trim) { php_do_trim(INTERNAL_FUNCTION_PARAM_PASSTHRU, 3); } PHP_FUNCTION(rtrim) { php_do_trim(INTERNAL_FUNCTION_PARAM_PASSTHRU, 2); } PHP_FUNCTION(ltrim) { php_do_trim(INTERNAL_FUNCTION_PARAM_PASSTHRU, 1); } static void php_do_trim(INTERNAL_FUNCTION_PARAMETERS, int mode) { zend_string *str; zend_string *what = NULL; ZEND_PARSE_PARAMETERS_START(1, 2) Z_PARAM_STR(str) Z_PARAM_OPTIONAL Z_PARAM_STR(what) ZEND_PARSE_PARAMETERS_END(); ZVAL_STR(return_value, php_trim(str, (what ? ZSTR_VAL(what) : NULL), (what ? ZSTR_LEN(what) : 0), mode)); } PHPAPI zend_string *php_trim(zend_string *str, char *what, size_t what_len, int mode) { const char *c = ZSTR_VAL(str); size_t len = ZSTR_LEN(str); register size_t i; size_t trimmed = 0; char mask[256]; if (what) { if (what_len == 1) { char p = *what; if (mode & 1) { for (i = 0; i < len; i++) { if (c[i] == p) { trimmed++; } else { break; } } len -= trimmed; c += trimmed; } if (mode & 2) { if (len > 0) { i = len - 1; do { if (c[i] == p) { len--; } else { break; } } while (i-- != 0); } } } else { php_charmask((unsigned char*)what, what_len, mask); if (mode & 1) { for (i = 0; i < len; i++) { if (mask[(unsigned char)c[i]]) { trimmed++; } else { break; } } len -= trimmed; c += trimmed; } if (mode & 2) { if (len > 0) { i = len - 1; do { if (mask[(unsigned char)c[i]]) { len--; } else { break; } } while (i-- != 0); } } } } else { if (mode & 1) { for (i = 0; i < len; i++) { if ((unsigned char)c[i] <= && (c[i] == || c[i] == \n || c[i] == \r || c[i] == \t || c[i] == \v || c[i] == \0)) { trimmed++; } else { break; } } len -= trimmed; c += trimmed; } if (mode & 2) { if (len > 0) { i = len - 1; do { if ((unsigned char)c[i] <= && (c[i] == || c[i] == \n || c[i] == \r || c[i] == \t || c[i] == \v || c[i] == \0)) { len--; } else { break; } } while (i-- != 0); } } } if (ZSTR_LEN(str) == len) { return zend_string_copy(str); } else { return zend_string_init(c, len, 0); } } /* { { { php_charmask * Fills a 256-byte bytemask with input. You can specify a range like a..z, * it needs to be incrementing. * Returns: FAILURE/SUCCESS whether the input was correct (i.e. no range errors) */static inline int php_charmask(unsigned char *input, size_t len, char *mask){ unsigned char *end; unsigned char c; int result = SUCCESS; memset(mask, 0, 256); for (end = input+len; input < end; input++) { c=*input; if ((input+3 < end) && input[1] == . && input[2] == . && input[3] >= c) { memset(mask+c, 1, input[3] - c + 1); input+=3; } else if ((input+1 < end) && input[0] == . && input[1] == .) { /* Error, try to be as helpful as possible: (a range ending/starting with . wont be captured here) */ if (end-len >= input) { /* there was no left char */ php_error_docref(NULL, E_WARNING, "Invalid ..-range, no character to the left of .."); result = FAILURE; continue; } if (input+2 >= end) { /* there is no right char */ php_error_docref(NULL, E_WARNING, "Invalid ..-range, no character to the right of .."); result = FAILURE; continue; } if (input[-1] > input[2]) { /* wrong order */ php_error_docref(NULL, E_WARNING, "Invalid ..-range, ..-range needs to be incrementing"); result = FAILURE; continue; } /* FIXME: better error (a..b..c is the only left possibility?) */ php_error_docref(NULL, E_WARNING, "Invalid ..-range"); result = FAILURE; continue; } else { mask[c]=1; } } return result;}/* }}} */