How to solve the problem of php trim garbled characters

php trim garbled code is because when executing rtrim, 0x81 will be removed, resulting in garbled code. The solution is to use the "mb_rtrim($tag, ",",$encoding)" method to solve the garbled code.

The operating environment of this article: windows7 system, PHP7.1 version, DELL G3 computer

First run the following code:

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

We may think that the result we will get is an Internet product, but the actual result is an Internet product. Why is this so?

Popular Science

All those using the mb_ prefix in PHP are multi-byte functions http://php.net/manual/zh/ref....

For example

$str = "abcd";
print_r(strlen($str).""); // 4
print_r(mb_strlen($str).""); // 4
$str = "周梦康";
print_r(strlen($str).""); // 9
print_r(mb_strlen($str).""); // 3

mb_ series functions operate based on the granularity of "one character composed of multiple bytes". Without mb_, they operate based on the actual number of bytes.

Principle

trim function documentation

string trim ( string $str [, string $character_mask = " " ] )

This function is not a multi-byte function, that is to say, multi-byte characters such as Chinese characters will have their heads or tails Use a single byte to match the char array corresponding to the subsequent $character_mask. If it is in the subsequent array, delete it and continue matching. For example:

echo ltrim("bcdf","abc"); // df

As shown in the function string_print_char in the demo below:

consists of three bytes 0xe3 0x80 0x81,

consists of three bytes 0xe5 0x93 0x81 composition.

So when executing rtrim, 0x81 will be removed through byte comparison, resulting in garbled characters in the end.

[Recommended study: "PHP Video Tutorial"]

Source code exploration

View the source code of PHP7, Then I extracted the following small demo to facilitate everyone to learn together. In fact, learning PHP source code is not difficult, and you can make a little progress every day.

//
// 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",ltrim("bcdf","abc"));
string_print_char("品"); // e5 93 81
string_print_char("、"); // e3 80 81
printf("%s",rtrim("互联网产品、","、"));
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 ",str[i]);
}
printf("");
}
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;
}
}

If you feel that the demo is not clear enough, copy it and execute it yourself~

C Students with poor language foundation don’t need to worry, I will write a special PHP tutorial for beginners later. A series of short introductory articles on C language.

Solution

Then let’s follow the same pattern and use PHP’s own multi-byte functions to implement it:

function mb_rtrim($string, $trim, $encoding)
{
$mask = [];
$trimLength = mb_strlen($trim, $encoding);
for ($i = 0; $i < $trimLength; $i++) {
$item = mb_substr($trim, $i, 1, $encoding);
$mask[] = $item;
}
$len = mb_strlen($string, $encoding);
if ($len > 0) {
$i = $len - 1;
do {
$item = mb_substr($string, $i, 1, $encoding);
if (in_array($item, $mask)) {
$len--;
} else {
break;
}
} while ($i-- != 0);
}
return mb_substr($string, 0, $len, $encoding);
}
mb_internal_encoding("UTF-8");
$tag = "互联网产品、";
$encoding = mb_internal_encoding();
print_r(mb_rtrim($tag, "、",$encoding));

Of course you You can also use regular expressions. Through the above function learning, have you learned single-byte functions and multi-byte functions?

PHP7 related source code

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] <= &#39; &#39; &&
(c[i] == &#39; &#39; || c[i] == &#39;&#39; || c[i] == &#39;&#39; || c[i] == &#39; &#39; || c[i] == &#39;&#39; || c[i] == &#39;&#39;)) {
trimmed++;
} else {
break;
}
}
len -= trimmed;
c += trimmed;
}
if (mode & 2) {
if (len > 0) {
i = len - 1;
do {
if ((unsigned char)c[i] <= &#39; &#39; &&
(c[i] == &#39; &#39; || c[i] == &#39;&#39; || c[i] == &#39;&#39; || c[i] == &#39; &#39; || c[i] == &#39;&#39; || c[i] == &#39;&#39;)) {
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 &#39;a..z&#39;,
* 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] == &#39;.&#39; && input[2] == &#39;.&#39;
&& input[3] >= c) {
memset(mask+c, 1, input[3] - c + 1);
input+=3;
} else if ((input+1 < end) && input[0] == &#39;.&#39; && input[1] == &#39;.&#39;) {
/* Error, try to be as helpful as possible:
(a range ending/starting with &#39;.&#39; won&#39;t be captured here) */
if (end-len >= input) { /* there was no &#39;left&#39; char */
php_error_docref(NULL, E_WARNING, "Invalid &#39;..&#39;-range, no character to the left of &#39;..&#39;");
result = FAILURE;
continue;
}
if (input+2 >= end) { /* there is no &#39;right&#39; char */
php_error_docref(NULL, E_WARNING, "Invalid &#39;..&#39;-range, no character to the right of &#39;..&#39;");
result = FAILURE;
continue;
}
if (input[-1] > input[2]) { /* wrong order */
php_error_docref(NULL, E_WARNING, "Invalid &#39;..&#39;-range, &#39;..&#39;-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 &#39;..&#39;-range");
result = FAILURE;
continue;
} else {
mask[c]=1;
}
}
return result;
}
/* }}} */

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