Last updated on March 28th, 2016 at 03:28 pm
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.
Symbol |
Explanation |
| \ | 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", "anehkumar@gmail.com");
you also use php filter_var() function to validate email
filter_var("anehkumar@gmail.com", 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!