PHP filtering and processing of special characters for form submission

One, several PHP functions related to special character processing

Name of function	Interpretation	Introduced
Htmlspecialchars	Combine with, single double quotes, greater than, and less than sign into HTML format	& Turn into &amp; "Turn into &quot; ' Turn into & #039; < turn into &lt; > Turn into &gt;
Htmlentities ()	All characters are converted to HTML format	In addition to the above Htmlspecialchars characters, the double-byte characters are displayed as encodings.
Addslashes	Single double quote, backslash, and null plus backslash escape	The characters that are changed include single quotation marks ('), double quotation marks ("), backslash backslash (\), and null character null.
Stripslashes	Remove backslash characters	Removes 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	The string that contains the. \\ + * ? [ ^ ] ($) to precede the character with the backslash "\" symbol.
NL2BR ()	Turn newline characters into <br>
Strip_tags	Remove HTML and PHP tags	Remove any HTML tags and PHP tags from the string, including the content between tags blocking. Note that if there is an error in the string HTML and PHP tags, an error will also be returned.
Mysql_real_escape_string	Escaping special characters in SQL strings	Escaped \x00 \ r \ n space \ ' "\x1a, which is useful for multibyte character processing. Mysql_real_escape_string will judge the character set, mysql_escape_string do not consider it.

For other string processing functions, refer to: Knowledge Sharing: PHP common string regular substitution and split function comparison.

PHP common Regular matching function between the differences, mainly Str_replace, Str_ireplace, Substr_replace, Preg_replace, Preg_match, Preg_match_all, Preg_quote, Preg_split, Ereg_replace, Eregi_replace, Preg_replace, Str_split, of course, a few of them can not use regular expressions, but because the relationship with the relevant regular function ambiguous so all put together to compare, convenient reference.

Name	Support Regular	Characteristics	Note
Str_replace	X	String substitution function, case sensitive
Str_ireplace	X	String substitution function, case insensitive, array-type batch substitution support	Thank netizens Franci, remind to add
Substr_replace	X	Partial substitution string function, you can specify the position index
Preg_replace	Y	Specifying a matching pattern for substitution, supporting substring references	Priority use
Ereg_replace	Y	Specify matching pattern for substitution, case sensitivity, support for substring references
Eregi_replace	Y	Specifies that the matching pattern is replaced, case insensitive, and supports substring references
Ereg	Y	Specifies the pattern full-text match, which can be used to match the judgment, or return a matching array
Preg_match	Y	Specifies whether the pattern matches one exit, which can be used to match the judgment, or to use the returned matching array	Priority use
Preg_match_all	Y	Specifies a pattern full-text match, typically used to return a matching array	Priority use
Preg_split	Y	Specifies the regular split in the matching mode, if it is best to use explode or str_split
Str_split	X	Specifies the length of the split string, by default a single character split into an array
Explode	X	You can specify a single or multiple character splitting string, and a successful return array, for example, 12345 returns 12 and 5 according to the 34 split
Preg_quote	-	Escape regular expression characters, meaning that special characters are prefixed with backslashes, and special characters for regular expressions include:. + * ? [ ^ ] $ ( ) { } = ! < > | : -

Additional notes:

1, there are two sets of regular expression function library in PHP, the function is very similar:

The set is provided by the POSIX (portable Operating System Interface of Unix) library, which is named after the Ereg_ prefix and is no longer recommended for POSIX regular libraries.

The set is provided by the Pcre (Perl Compatible Regular Expression) library, which is named after the Preg_ prefix and is recommended for priority use. In Pcre, a pattern expression (that is, a regular expression) is typically included between two backslashes "/", such as the "/^w+$/" style.

2, PHP Regular expression function: matching extraction, matching replacement.

PHP filtering and processing of special characters for form submission