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Regex to match anything

I know it seems a bit redundant but I’d like a regex to match anything. At the moment we are using ^*$ but it doesn’t seem to match no matter what the text. I do a manual check for no text but the test view we use is always validated with a regex. However, sometimes we need it to validate anything using a regex. i.e. it doesn’t matter what is in the text field, it can be anything. I don’t actually produce the regex and I’m a complete beginner with them.

4 Answers 4

The regex .* will match anything (including the empty string, as Junuxx points out).

Checking for nothing doesn’t matter too much as I’m doing that outside of the regex. I will try both though, thanks.

The chosen answer is slightly incorrect, as it wont match line breaks or returns. This regex to match anything is useful if your desired selection includes any line breaks:

[\s\S] matches a character that is either a whitespace character (including line break characters), or a character that is not a whitespace character. Since all characters are either whitespace or non-whitespace, this character class matches any character. the + matches one or more of the preceding expression

^ is the beginning-of-line anchor, so it will be a «zero-width match,» meaning it won’t match any actual characters (and the first character matched after the ^ will be the first character of the string). Similarly, $ is the end-of-line anchor.

* is a quantifier. It will not by itself match anything; it only indicates how many times a portion of the pattern can be matched. Specifically, it indicates that the previous «atom» (that is, the previous character or the previous parenthesized sub-pattern) can match any number of times.

To actually match some set of characters, you need to use a character class. As RichieHindle pointed out, the character class you need here is . , which represents any character except newlines (and it can be made to match newlines as well using the appropriate flag). So .* represents * (any number) matches on . (any character). Similarly, .+ represents + (at least one) matches on . (any character).

Источник

PHP Regular Expressions

A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for.

A regular expression can be a single character, or a more complicated pattern.

Regular expressions can be used to perform all types of text search and text replace operations.

Syntax

In PHP, regular expressions are strings composed of delimiters, a pattern and optional modifiers.

In the example above, / is the delimiter, w3schools is the pattern that is being searched for, and i is a modifier that makes the search case-insensitive.

The delimiter can be any character that is not a letter, number, backslash or space. The most common delimiter is the forward slash (/), but when your pattern contains forward slashes it is convenient to choose other delimiters such as # or ~.

Regular Expression Functions

PHP provides a variety of functions that allow you to use regular expressions. The preg_match() , preg_match_all() and preg_replace() functions are some of the most commonly used ones:

Function	Description
preg_match()	Returns 1 if the pattern was found in the string and 0 if not
preg_match_all()	Returns the number of times the pattern was found in the string, which may also be 0
preg_replace()	Returns a new string where matched patterns have been replaced with another string

Using preg_match()

The preg_match() function will tell you whether a string contains matches of a pattern.

Example

Use a regular expression to do a case-insensitive search for «w3schools» in a string:

Using preg_match_all()

The preg_match_all() function will tell you how many matches were found for a pattern in a string.

Example

Use a regular expression to do a case-insensitive count of the number of occurrences of «ain» in a string:

$str = «The rain in SPAIN falls mainly on the plains.»;
$pattern = «/ain/i»;
echo preg_match_all($pattern, $str); // Outputs 4
?>

Using preg_replace()

The preg_replace() function will replace all of the matches of the pattern in a string with another string.

Example

Use a case-insensitive regular expression to replace Microsoft with W3Schools in a string:

$str = «Visit Microsoft!»;
$pattern = «/microsoft/i»;
echo preg_replace($pattern, «W3Schools», $str); // Outputs «Visit W3Schools!»
?>

Regular Expression Modifiers

Modifiers can change how a search is performed.

Modifier	Description
i	Performs a case-insensitive search
m	Performs a multiline search (patterns that search for the beginning or end of a string will match the beginning or end of each line)
u	Enables correct matching of UTF-8 encoded patterns

Regular Expression Patterns

Brackets are used to find a range of characters:

Expression	Description
[abc]	Find one character from the options between the brackets
[^abc]	Find any character NOT between the brackets
4	Find one character from the range 0 to 9

Metacharacters

Metacharacters are characters with a special meaning:

Metacharacter	Description
|	Find a match for any one of the patterns separated by | as in: cat|dog|fish
.	Find just one instance of any character
^	Finds a match as the beginning of a string as in: ^Hello
$	Finds a match at the end of the string as in: World$
\d	Find a digit
\s	Find a whitespace character
\b	Find a match at the beginning of a word like this: \bWORD, or at the end of a word like this: WORD\b
\uxxxx	Find the Unicode character specified by the hexadecimal number xxxx

Quantifiers

Quantifiers define quantities:

Quantifier	Description
n+	Matches any string that contains at least one n
n*	Matches any string that contains zero or more occurrences of n
n?	Matches any string that contains zero or one occurrences of n
n	Matches any string that contains a sequence of X n‘s
n	Matches any string that contains a sequence of X to Y n‘s
n	Matches any string that contains a sequence of at least X n‘s

Note: If your expression needs to search for one of the special characters you can use a backslash ( \ ) to escape them. For example, to search for one or more question marks you can use the following expression: $pattern = ‘/\?+/’;

Grouping

You can use parentheses ( ) to apply quantifiers to entire patterns. They also can be used to select parts of the pattern to be used as a match.

Example

Use grouping to search for the word «banana» by looking for ba followed by two instances of na:

Complete RegExp Reference

The reference contains descriptions and examples of all Regular Expression functions.

Источник

regex to match any string whether Unicode or not?

If your PCRE is compiled with unicode support, you can just match against the letter space from the unicode standard.

Please note the u-modifier, that enables unicode matching.

$string = ""; $pattern = '/"; $pattern = '/