PHP Summary of the filtering and processing of special characters for form submission _php tips

PHP on the form to submit special characters of the processing method to do a summary, mainly related to Htmlspecialchars/addslashes/stripslashes/strip_tags/mysql_real_escape_ Several functions, such as String, are used jointly to communicate with others.

One or several PHP functions related to special character processing

The name of the function	Interpretation	Introduced
Htmlspecialchars	Converts to HTML format with, single double quotes, greater than and less than	& Turn & "Turn" ' Turn ' < Turn < > Turn >
Htmlentities ()	All characters are converted to HTML format	In addition to the above Htmlspecialchars characters, also include double-byte characters to display the encoding and so on.
Addslashes	Single double quotes, backslash and null plus backslash escape	The changed characters include single quotation marks ('), double quotes ("), backslash backslash (\), and null character nulls.
Stripslashes	Remove backslash characters	Remove the backslash character from the string. If you have two consecutive backslashes, remove one and leave one. If there is only one backslash, remove it directly.
Quotemeta	Add Reference symbol	Contains the string. \\ + * ? [ ^ ] ($) Precede the character with the backslash "\" symbol.
NL2BR ()	Convert newline characters to
Strip_tags	Remove HTML and PHP tags	Remove any HTML tags and PHP tags from the string, including marking the contents between the blocking. Note If there are errors in the string HTML and PHP tags, an error is returned.
Mysql_real_escape_string	Escape a special character in a SQL string	The escape \x00 \ r \ n space \ ' "\X1A is effective for multibyte character processing. Mysql_real_escape_string will judge the character set, and mysql_escape_string is not to be considered.