It is special chacter(s) which have special meaning in Regular Expression.

For Example:
*, ., /, \, ? and ^.

Sr Meta character Desctiption
1 [ ] Match any character within [phc]
Means find “p” OR “h” OR “c”
2 Range
a-z means a to z(a,b,c, … z)

0-0 means 0 to 9 (0,1,2,3,4,5,6,7,8,9)

A-Z means A to Z(A,B,C,D ….. Z)

3 ^ Caret It means start with a character

For example: ^ab (start with “a”)

Inside the bracket if have opposite meaning.

For example: [^a](must not start with “a”)

4 $ End with character

For Example

Abc$ means end with “c”

5 . The . (period) means any character(s) in this position,
For example, ph. will find php, php-tutorial and php-tutorial-php but not aphp because it has no following character
6 ? Matches the preceding character 0 or 1 times only.

For example:

colou?r will find both color (0 times) and colour (1 time).

7 * Matches the preceding character 0 or more times.
For example:

tre* will find tree (2 times) and tread (1 time) and trough (0 times).

8 + Matches the previous character 1 or more times.
For example:

tre+ will find tree (2 times) and tread (1 time) but NOT trough (0 times).

9 {n} Preceding character, or character range, n times exactly.
For example:

find a local phone number we could use [0-9]{3}-[0-9]{4} which would find any number of the form 723-4567 OR 132-3234 OR 214-3433.

10 () To group a character.

For Example:
(php), will find the “php” only.

11 | Vertical bar used for OR

(a|c) find either “a” OR “c”

12 \d any character in the range 0 – 9
13 \D Any character not in between 0-9
14 \s Whitespace or tab
15 \S Not whitespace or tab
16 \w Alphanumeric characters (a-z, 0-9, A-Z)
17 \W Not alphanumeric character (a-z, 0-9, A-Z)
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