Neozeratul en la Red

En Sentido Web han publicado 5 expresiones regulares que nos pueden ser útiles a todos los desarrolladores web y es que con una sola expresion regular bien implementada podemos ahorrarnos varias lineas de código.

Comprobar que una cadena solo contenga carateres alfanumericos y que la longitud este entre 3 y 16.

1. /^[a-zA-Z0-9_]{3,16}$/

Ejemplo de Uso en PHP

1. function validate_username( $username ) {

2. if(preg_match(‘/^[a-zA-Z0-9_]{3,16}$/’, $_GET[‘username’])) {

3. return true;

4. }

5. return false;

6. }

Encontrar una etiqueta XHTML o XML

• {<tag[^>]*>(.*?)</tag>}

Etiqueta XHTML o XML con atributos

• {<tag[^>]*attribute\s*=\s*([”‘])value\\1[^>]*>(.*?)</tag>}

Verificar Dirección de Correo Electrónico (Email)

1. function is_valid_email_address($email){

2. $qtext = ‘[^\x0d\x22\x5c\x80-\xff]’;

3. $dtext = ‘[^\x0d\x5b-\x5d\x80-\xff]’;

4. $atom = ‘[^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c’.

5. ‘\x3e\x40\x5b-\x5d\x7f-\xff]+’;

6. $quoted_pair = ‘\x5c[\x00-\x7f]’;

7. $domain_literal = “\x5b($dtext|$quoted_pair)*\x5d”;

8. $quoted_string = “\x22($qtext|$quoted_pair)*\x22″;

9. $domain_ref = $atom;

10. $sub_domain = “($domain_ref|$domain_literal)”;

11. $word = “($atom|$quoted_string)”;

12. $domain = “$sub_domain(\x2e$sub_domain)*”;

13. $local_part = “$word(\x2e$word)*”;

14. $addr_spec = “$local_part\x40$domain”;

15.  

16. return preg_match(“!^$addr_spec$!”, $email) ? 1 : 0;

17. }

Validar URL 

1. {

2. \b

3. # Match the leading part (proto://hostname, or just hostname)

4. (

5. # http://, or https:// leading part

6. (https?)://[-\w]+(\.\w[-\w]*)+

7. |

8. # or, try to find a hostname with more specific sub-expression

9. (?i: [a-z0-9] (?:[-a-z0-9]*[a-z0-9])? \. )+ # sub domains

10. # Now ending .com, etc. For these, require lowercase

11. (?-i: com\b

12. | edu\b

13. | biz\b

14. | gov\b

15. | in(?:t|fo)\b # .int or .info

16. | mil\b

17. | net\b

18. | org\b

19. | [a-z][a-z]\.[a-z][a-z]\b # two-letter country code

20. )

21. )

22.  

23. # Allow an optional port number

24. ( : \d+ )?

25.  

26. # The rest of the URL is optional, and begins with /

27. (

28. /

29. # The rest are heuristics for what seems to work well

30. [^.!,?;“\’&lt;&gt;()[]{}sx7F-\xFF]*

31. (

32. [.!,?]+ [^.!,?;”\���&lt;&gt;()\[\]{\}s\x7F-\xFF]+

33. )*

34. )?

35. }ix