Summary of PHP filtering and processing methods for form submission special characters_PHP tutorial

Here is a summary of PHP’s methods for handling special characters in form submissions, which mainly involve the joint use of several functions such as htmlspecialchars/addslashes/stripslashes/strip_tags/mysql_real_escape_string, and share with everyone.

1. Several PHP functions related to special character processing

Function name

函数名	释义	介绍
htmlspecialchars	将与、单双引号、大于和小于号化成HTML格式	&转成& "转成" ' 转成' >转成>
htmlentities()	所有字符都转成HTML格式	除上面htmlspecialchars字符外，还包括双字节字符显示成编码等。
addslashes	单双引号、反斜线及NULL加上反斜线转义	被改的字符包括单引号(')、双引号(")、反斜线backslash () 以及空字符NULL。
stripslashes	去掉反斜线字符	去掉字符串中的反斜线字符。若是连续二个反斜线，则去掉一个，留下一个。若只有一个反斜线，就直接去掉。
quotemeta	加入引用符号	将字符串中含有. \ + * ? [ ^ ] ( $ ) 等字符的前面加入反斜线"" 符号。
nl2br()	将换行字符转成
strip_tags	去掉HTML及PHP标记	去掉字符串中任何HTML标记和PHP标记，包括标记封堵之间的内容。注意如果字符串HTML及PHP标签存在错误，也会返回错误。
mysql_real_escape_string	转义SQL字符串中的特殊字符	转义x00 n r 空格 ' " x1a，针对多字节字符处理很有效。mysql_real_escape_string会判断字符集，mysql_escape_string则不用考虑。

Definition

Introduction

htmlspecialchars

Convert ampersands, single and double quotation marks, greater than and less than signs into HTML format

&Convert&"Convert"' Convert to'>Convert>

htmlentities()

All characters are converted to HTML format

In addition to the htmlspecialchars characters above, it also includes double-byte characters displayed as encodings, etc.

addslashes

Single and double quotes, backslashes and NULL plus backslash escape

The modified characters include single quotes ('), double quotes ("), backslash () and the empty character NULL.

stripslashes

Remove backslash characters

Remove backslash characters in the string. If there are two consecutive backslashes, remove one and leave one. If there is only one backslash, just remove it.

quotemeta

Add quotation marks

Add the backslash "" symbol in front of characters such as \ + * ? [ ^ ] ( $ ) in the string.

nl2br()

Convert newline characters to

strip_tags

Remove HTML and PHP tags

Remove any HTML tags and PHP tags in the string, including the content between tag blocks. Note that if there are errors in the string HTML and PHP tags, errors will also be returned.

mysql_real_escape_string

Escape special characters in SQL strings

Escape x00 n r space ' " x1a, very effective for multi-byte character processing. mysql_real_escape_string will determine the character set, but mysql_escape_string does not need to be considered.

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