How do I use PHP's preg_match to validate strings?

Question

Please tell me how to use the various symbols used for expression matching in preg_match function of PHP.

Besides basic information, please give example for checking a valid e-mail address and a string that should not contain / : ; { } * &

Answer 1

this is the best set of introductory regex information I've seen recently.

Answer 2

Jeff Atwood recently had an article on his coding horror blog about regular expressions. Check out "Regular Expressions for Regular Programmers".

Answer 3

To check for a valid mail you can either use build in functionality (filter_var()/FILTER_VALIDATE_EMAIL) or use nice ready to use libraries which are compliant to the current RFC. PHP : Parsing Email Adresses in PHP. For examples on preg_match() you can go to the php website and a full list regular expression options is available on Wikipedia. To learn about Regex I recommend "The Regex Coach".

Answer 4

Simple example.. Verifying $var which is a string verifying and checking for (a to z AND A to Z) characters.

<?php
$var = 'hello';
if (ereg("[a-zA-Z]", $var)) {
  echo 'it was typed correctly';
} else {
  echo 'it was not typed correctly';
}
?>

more regular expressions syntax exemples: http://www.regexlib.com/

EDIT:

if (ereg("^([0-9,a-z,A-Z]+)([.,_]([0-9,a-z,A-Z]+))*[@]([0-9,a-z,A-Z]+)([.,_,-]([0-9,a-z,A-Z]+))*[.]([0-9,a-z,A-Z]){2}([0-9,a-z,A-Z])?$", $email)) {

  echo 'email ok';

} else {

  echo 'email not ok';

}

Regards.

Answer 5

I know the question is about PHP, but my purpose is to illustrate the intricacies of email address validation: To check if an email address conforms to RFC 2822, you can use the Perl module Email::Address. Do take a look at the source of that module as well as the RFC.

Answer 6

If I give $var = 'hello87%^$' also returning "it was typed correctly";