Regular expression is very important when you need to validate data. But Regular expression is not easy to understand for biginners. In this tut i will explain you how we can create regular expression and also tell some expression which we regular use for form validation.

List of symbols we used in regular expression.



\ Escape Special characters.
. Match a single character of any value, except end of line.
^ Match the start of the line.
$ Match the end of the line.
| Match either the regular expression preceding it or the regular expression following it.
[ ] Match any single character from within the bracketed.
! Do not match the next character or regular expression.
? Match 0 or 1 time.
* Match 0 or more times.
+ Match 1 or more times.

Now we use these symbol and create some basic regular expressions.

Regular Expression to check integer no

preg_match('/^[0-9]*$/', '1234');

Regular Expression to check character value without space

preg_match('/^[a-z]*$/', 'abc');

Regular Expression to check lower and upper case letter

preg_match('/^[a-zA-Z]*$/', 'Aabc');

Regular Expression to check lower and uppercase letter and integer and also white space

preg_match('/^[a-z0-9 ]*$/i', 'trinity Canyon 01');

Expression to validate email address

preg_match("/^[\.A-z0-9_\-\+]+[@][A-z0-9_\-]+([.][A-z0-9_\-]+)+[A-z]{1,4}$/i", "[email protected]");

you also use php filter_var() function to validate email

filter_var("[email protected]", FILTER_VALIDATE_EMAIL)

Now some other regular expression

\A     Start of string
\z     End of string
\s     Any whitespace character
\S     Any non-whitespace character
\d     Any digit
\D     Any non-digit
\w     Any word character (letter, number, underscore)
\W     Any non-word character
\b     Any word boundary character
(…)     Capture everything enclosed
(a|b)     a or b
a{3}     Exactly 3 of a
a{3,}     3 or more of a
a{3,6}     Between 3 and 6 of a

These are simple and easy example of regular and working expression.

Happy Coading!