Last updated: Tue, 27 Nov 2007

Funciones de Expresiones Regulares (POSIX Extendido)

Introducción

Tip

PHP ofrece también soporte de expresiones regulares usando una sintaxis compatible con Perl usando las Funciones PCRE. Tales funciones soportan coincidencias no-ambiciosas, aserciones, subpatrones condicionales, y un número de características adicionales que no son soportadas por las sintaxis de expresiones regulares POSIX-extendido.

Warning

Estas expresiones regulares no son seguras con material binario. Las Funciones PCRE lo son.

Las expresiones regulares son usadas para la manipulación compleja de cadenas. PHP usa expresiones regulares POSIX extendidas, tal y como se definen por POSIX 1003.2. Para una descripción completa de las expresiones regulares POSIX, vea las » páginas de manual de regex incluidas en el directorio regex en la distribución de PHP. Se encuentran en formato manpage, así que querrá hacer algo del estilo de man /usr/local/src/regex/regex.7 para leerlas.

Requisitos

No se necesitan bibliotecas externas para construir esta extensión

Instalación

Warning

No modifique el TIPO a menos que sepa lo que está haciendo.

Para habilitar el soporte para expresiones regulares, configure PHP con la opción --with-regex[=TIPO]. TIPO puede ser un valor entre system, apache, php. La acción predeterminada es usar php.

La versión para Windows de PHP tiene soporte nativo para esta extensión. No se necesita cargar ninguna extensión adicional para usar estas funciones.

Configuración en tiempo de ejecución

Esta extensión no tiene directivas de configuración en php.ini.

Tipos de recursos

Esta extensión no tiene ningún tipo de recurso definido.

Constantes predefinidas

Esta extensión no tiene ninguna constante definida.

Ejemplos

Example#1 Ejemplos de Expresiones Regulares


<?php
// Devuelve true si "abc" se encuentra en cualquier lugar de $cadena.
ereg("abc", $cadena);

// Devuelve true si "abc" es encontrado al comienzo de $cadena
ereg("^abc", $cadena);

// Devuelve true si "abc" es encontrado al final de $cadena.
ereg("abc$", $cadena);

// Devuelve true si el navegador del cliente es Netscape 2, 3 or MSIE 3.
eregi("(ozilla.[23]|MSIE.3)", $_SERVER["HTTP_USER_AGENT"]);

// Coloca tres palabras separadas por espacios en $regs[1], $regs[2] y $regs[3].
ereg("([[:alnum:]]+) ([[:alnum:]]+) ([[:alnum:]]+)", $cadena, $regs);

// Coloca una etiqueta <br /> al comienzo de $cadena.
$cadena = ereg_replace("^", "<br />", $cadena);

// Coloca una etiqueta <br /> al final de $cadena.
$cadena = ereg_replace("$", "<br />", $cadena);

// Se deshace de cualquier caracter de salto de línea en $cadena.
$cadena = ereg_replace("\n", "", $cadena);
?>

Ver también

Para consultar sobre expresiones regulares en una sintaxis compatible con Perl, eche un vistazo a las Funciones PCRE. Las coincidencias más simples de comodines tipo intérprete de comandos son ofrecidas por fnmatch().

ereg_replace — reemplaza expresiones regulares
ereg — Coincidencia de expresiones regulares
eregi_replace — reemplaza expresiones regularse sin diferenciar mayúsculas y minúsculas
eregi — coincidencia de expresiones regulares sin diferenciar mayúsculas y minúsculas
split — divide la cadena en elementos de un array según una expresión regular
spliti — Separar una cadena en una matriz mediante una expresión regular, no sensible a mayúsculas ni minúsculas
sql_regcase — construye una expresión regular para buscar coincidencias sin diferenciar mayúsculas y minúsculas

ereg_replace

posix_uname

Last updated: Tue, 27 Nov 2007

add a note User Contributed Notes
Regex POSIX

goran at extensionsforjoomla dot com
10-Sep-2007 05:04


@regex - off-topic date validator yyyy-mm-dd (mySQL date format)

try validating 2008-01-31 and it will fail.

Perhaps using core PHP functions and simple solutions could be better approach:

function validateDate($date)

{

  if (preg_match('/^(\d{4})-(\d{2})-(\d{2})$/', $date, $datebit)) :

    if (true === checkdate($datebit[2] , $datebit[3] , $datebit[1])) :

      return $date;

    endif;

  else :

    return false;

  endif;

}

17-May-2007 01:55


To exclude a word you can you derive from the following:



This checks that no table tag appears between my open and close td tags.



<td>((?!<table>).{1})*</td>

Edward Z. Yang
01-Apr-2007 08:16


The fact that 'regex' functions are not binary safe have some very important security implications for people who are using ereg to validate their input data.



Suppose I have an expression:



<?php

$pattern = '^[[:alnum:]]*$';

?>



This should match any number of alphanumeric characters, right? Well, if the string you're matching is not binary, sure. However, say we have a null-byte tossed in the string:



<?php

$string = chr(0) . "<script>alert('xss')</script>";

echo ereg($pattern, $string);

?>



Will return true. Note that it is trivially easy to inject null bytes into PHP parameters:



index.php?content=%00ASCII



Scary. So unless you really know what you're doing, just use the PCRE preg_* functions.

nate[-at-]theklaibers[-dot-]com
07-Feb-2006 10:19


I am using a regex with the same thought process in mind as the earlier phone number. However, I have also implemented it to allow the '1' so a number like.



1 222 222 2222 would still be valid as well (along with all of the other combinations.



In my regex, I pull out the matches - not the exact string. So if someone were to forget a bracket, it wouldnt matter to the actual output as it is stripped from that match.



So, if you put in 222) 233 3454, the matches would only pull out 1=>222, 2=>233, 3=>3454



This has been very helpful in tweaking my regex.



Thanks,

Nate

ajd at cloudiness dot com
23-Aug-2005 07:05


A minor tweak to trucex' phone validator, because some people use a dot separator between the area code, exchange and four-digit block.

Posted here for your copy-and-paste convenience.



$regex = '^[(]?[2-9]{1}[0-9]{2}[) -.]{0,2}' . '[0-9]{3}[- .]?' . '[0-9]{4}[ ]?' . '((x|ext)[.]?[ ]?[0-9]{1,5})?$';

nothing at nothing dot com
30-Jul-2005 01:35


His regular expression is correct, the ^ is to check for the beginning of the string. It is just looking for delimiter characters, try putting slashes around it.

"/<regex>/"

stringer at stringerstudios dot com
29-Jul-2005 03:07


Hey trucex. Cool phone number function but your $regex produces the following error. Warning: No ending delimiter '^' found



Instead of:

$regex = '^[(]?[2-9]{1}[0-9]{2}[) -]{0,2}' . '[0-9]{3}[- ]?' . '[0-9]{4}[ ]?' . '((x|ext)[.]?[ ]?[0-9]{1,5})?$';



It think should be:

$regex = '^[(]?[2-9]{1}[0-9]{2}[) -]{0,2}' . '[0-9]{3}[- ]?' . '[0-9]{4}[ ]?' . '((x|ext)[.]?[ ]?[0-9]{1,5})?$^';

trucex[at] gmail
27-Jul-2005 09:00


I was having a ton of issues with other people's phone number validation expressions, so I made my own. It works with most US phone numbers, including those with extentions. Format matches any of the following formats:



5551234567

555 1234567

555 123 4567

555 123-4567

555-1234567

555-123-4567

555123-4567

(555)1234567

(555)123 4567

(555)123-4567

(555) 1234567

(555) 123-4567

(555) 123 4567



And any of the following extentions can be added with or without a space between them and the number:

x123

x.123

x. 123

x 123

ext.123

ext. 123

ext 123

ext123



Extentions support between 1 and 5 digits. 



Here is the expression:



$regex = '^[(]?[2-9]{1}[0-9]{2}[) -]{0,2}' . '[0-9]{3}[- ]?' . '[0-9]{4}[ ]?' . '((x|ext)[.]?[ ]?[0-9]{1,5})?$';



Enjoy!

php at erikjan dot net
19-Feb-2005 02:28


To add to tgt's tip for metacharacters.

To test for a whole word, use [[:<:]]yourword[[:>:]]

franck569 at free dot fr
31-Jan-2005 05:14


if you want to exclude a WORD, use this :



[^[WORD]]{0}



@++, Franck569.

annie
09-Sep-2004 03:17


Another nice tuturial about regular expressions: http://www.mkssoftware.com/docs/man5/regexp.5.asp

tgt at tip dot nl
08-Sep-2004 12:17


Tip !

Metacharacters in regular expresions are usefull and easy to use.



The following is a set of special values that denote certain common ranges. They have the advantage that also take in account the 'locale' i.e. any variant of the local language/coding system.



[:digit:]      Only the digits 0 to 9 

[:alnum:]      Any alphanumeric character 0 to 9 OR A to Z or a to z. 

[:alpha:]       Any alpha character A to Z or a to z. 

[:blank:]       Space and TAB characters only. 

[:xdigit:]     . 

[:punct:]       Punctuation symbols . , " ' ? ! ; : 

[:print:]      Any printable character. 

[:space:]      Any space characters. 

[:graph:]       . 

[:upper:]       Any alpha character A to Z. 

[:lower:]       Any alpha character a to z. 

[:cntrl:]        .

mina86 at tlen dot pl
19-Oct-2003 07:14


I tested how fast POSIX and Perl regular expresions are, and here are the results:



           | POSIX Extended  | Perl-Compatible |   POSIX - Perl

-----------+-----------------+-----------------+-----------------

     match |    0.1296420097 |    0.1006720066 |  0.0289700031

   match i |    0.1204010248 |    0.1101620197 |  0.0102390051

   replace |    0.1896649599 |    0.1298999786 |  0.0597649813

 replace i |   10.6998120546 |    0.1453789473 | 10.5544331074



So, as you can see, preg_* functions are faster then ereg* functions. You can find source code of my test script here: http://mina86.home.staszic.waw.pl/temp/regexp-speed-test.txt

Robin
15-Jan-2003 08:53


Ever wondered how to exclude "[" and "]"?

Here it goes: "[^][]". Extra characters to exclude can beadded right in the middle like this: "[^]fobar[]".

moc DOT liamtoh AT ssengnorw
18-Oct-2002 06:28


In a PCRE \s matches whitespace, but not inside a character class:



preg_match ('/\s/', ' ') // match

preg_match ('/[\s]/', ' ') // no match



Within a character class [:space:] is treated as a single character that matches any single whitespace character:



$pattern = '/[[:space:]]/';

$subject = "space tab\tnewline\n";

preg_match_all($pattern, $subject, $out) // == 3



To match a hyphen from within a character class, it must either be first or last; otherwise, it will act as a range operator.



Example: To match a blank string or a string containing only uppercase letters, underscores, spaces, and hyphens:



preg_match('/^[A-Z_ -]*$/', $subject)



To match any whitespace, not just spaces:



preg_match('/^[A-Z_[:space:]-]*$/', $subject)

paper
09-Sep-2002 09:57


I have also experienced the same problem as bps7j@yahoo.com had been experiencing, except I did not recognize the problem until after many hours of debugging.



"\s" does not seem to represent spaces, however "[[:space:]]" does.



Another problem I was having was matching dashes/hyphens '-'. You must escape them "\-" and place them at the end of a bracket expression.



Example: To match a blank string or a string containing only uppercase letters, underscores, spaces, and hyphens:



^([A-Z_\-]|[[:space:]])*$



Hope this saves someone some time from debugging like I was. :)

bps7j at yahoo dot com
22-Aug-2002 05:40


Something that really got me: I'm used to using Perl's regexps, and so I used \s to check for a whitespace character in a password on a website. My PHP book (Wrox Press, Professional PHP Programming) agreed with me that this is exactly the same as [ \r\n\t\f\v], but it's NOT. In fact, what it did was keep anyone from joining the site if they put an 's' in their password! So beware, check for subtle differences between what you're used to and PHP.



[[:space:]] works fine, by the way.



I'm going to use the pcre functions from now on... I like Perl :o)

david at NOgreenhammerSPAM dot com
09-Mar-2002 08:40


Sadly, the Posix regexp evaluator (PHP 4.1.2) does not seem to support multi-character coallating sequences, even though such sequences are included in the man-page documentation.



Specifically, the man-page discusses the expression "[[.ch.]]*c" which matches the first five characters of "chchcc".  Running this expression in ereg_replace generates the error "Warning: REG_ECOLLATE".  (Running an equivalent expression with only one character between the periods does work, however.)



Multi-character coallating sequences are not supported!



This is really, really too bad, because it would have provided a simple way to exlude words from the target.



I'm going to go learn PCRE, now.  :-(

regex at dan42 dot cjb dot net
08-Mar-2002 08:33


Follow-up to my previous post:

Some simple optimization allowed me to realize that excluding a word at the beginning of a string has a degree of complexity O(n) rather than O(n^2). I only had to follow the logic:



if str[0] != badword[0] then OK

else

  if str[1] != badword[1] then OK

  else

    if str[2] != badword[2] then OK

    else ...



So excluding the word 'abc' at the beginning of a string is much more simple than I had made it out to be:

  ^([^a]|a[^b]|ab[^c])

spiceee at potentialvalleys dot com
07-Mar-2002 08:26


sorry to be picky here but saying ^ is beginning of a line or $ is end of line is rather misleading, if you're working on a daily basis with regexes.



it might be that it is most of the time correct BUT in some occasions you'd be better off to think of ^ as "start of string" and $ as "end of string".



there are ways to make your regex engine forget about your system's notion of a newline, it's what is commonly refered to as multiline regexes...

luciano_at_braziliantranslation.net
03-Mar-2002 10:15


mholdgate wrote a very nice quick reference guide in the next page (http://www.php.net/manual/en/function.ereg.php), but I felt it could be improved a little:

________________



^        Start of line

$        End of line

n?        Zero or only one single occurrence of character 'n'

n*        Zero or more occurrences of character 'n'

n+        At least one or more occurrences of character 'n'

n{2}        Exactly two occurrences of 'n'

n{2,}        At least 2 or more occurrences of 'n'

n{2,4}        From 2 to 4 occurrences of 'n'

.        Any single character

()        Parenthesis to group expressions

(.*)        Zero or more occurrences of any single character, ie, anything!

(n|a)        Either 'n' or 'a'

[1-6]        Any single digit in the range between 1 and 6

[c-h]        Any single lower case letter in the range between c and h

[D-M]        Any single upper case letter in the range between D and M

[^a-z]        Any single character EXCEPT any lower case letter between a and z.



        Pitfall: the ^ symbol only acts as an EXCEPT rule if it is the 

        very first character inside a range, and it denies the 

        entire range including the ^ symbol itself if it appears again 

        later in the range. Also remember that if it is the first 

        character in the entire expression, it means "start of line". 

        In any other place, it is always treated as a regular ^ symbol.

        In other words, you cannot deny a word with ^undesired_word 

        or a group with ^(undesired_phrase).

        Read more detailed regex documentation to find out what is 

        necessary to achieve this.



[_4^a-zA-Z]    Any single character which can be the underscore or the 

        number 4 or the ^ symbol or any letter, lower or upper case



?, +, * and the {} count parameters can be appended not only to a single character, but also to a group() or a range[].



therefore,

^.{2}[a-z]{1,2}_?[0-9]*([1-6]|[a-f])[^1-9]{2}a+$

would mean:



^.{2}         = A line beginning with any two characters, 

[a-z]{1,2}     = followed by either 1 or 2 lower case letters, 

_?         = followed by an optional underscore, 

[0-9]*         = followed by zero or more digits, 

([1-6]|[a-f])     = followed by either a digit between 1 and 6 OR a 

        lower case letter between a and f, 

[^1-9]{2}     = followed by any two characters except digits 

        between 1 and 9 (0 is possible), 

a+$         = followed by at least one or more 

        occurrences of 'a' at the end of a line.

regex at dan42 dot cjb dot net
21-Feb-2002 07:12


It's easy to exclude characters but excluding words with a regular expression is a bit more tricky. For parentheses there is no equivalent to the ^ for brackets. The only way I've found to exclude a string is to proceed by inverse logic: accept all the words that do NOT correspond to the string. So if you want to accept all strings except those _begining_ with "abc", you'd have to accept any string that matches one of the following:

  ^(ab[^c])

  ^(a[^b]c)

  ^(a[^b][^c])

  ^([^a]bc)

  ^([^a]b[^c])

  ^([^a][^b]c)

  ^([^a][^b][^c])



which, put together, gives the regex

  ^(ab[^c]|a[^b]c|a[^b][^c]|[^a]bc|[^a]b[^c]|[^a][^b]c|[^a][^b][^c])



Note that this won't work to detect the word "abc" anywhere in a string. You need to have some way of anchoring the inverse word match

like: ^(a[^b]|[^a]b|[^a][^b])   ;"ab" not at begining of line

  or: (a[^b]|[^a]b|[^a][^b])&   ;"ab" not at end of line

  or: 123(a[^b]|[^a]b|[^a][^b]) ;"ab" not after "123"



I don't know why "(abc){0,0}" is an invalid synthax. It would've made all this much simpler.

 

 

Slightly off-topic, here's a regex date validator (format yyyy-mm-dd, remove all spaces and linefeeds):

  ^(19|20)([0-9]{2}-((0[13-9]|1[0-2])-(0[1-9]|[12][0-9]|30)|

  (0[13578]|1[02])-31|02-(0[1-9]|1[0-9]|2[0-8]))|([2468]0|

  [02468][48]|[13579][26])-02-29)$

03-Feb-2002 05:02


if you are looking for the abbreviations like tab, carriage return, regex-class definitions  



you should look here: 

http://elvin.dstc.edu.au/doc/regex.html



some excerpts:



    \a    control characters bell

    \b    backspace

    \f    form feed

    \n    line feed

    \r    carriage return

    \t    horizontal tab

    \v    vertical tab



class example

    \cLu    all uppercase letters

bart at framers dot nl
07-Mar-2001 04:53


Dario seems to have made a nice tutorial about regular expressions:





http://www.phpbuilder.com/columns/dario19990616.php3





Thanks Dario! ...

add a note

ereg_replace

posix_uname

Last updated: Tue, 27 Nov 2007

Funciones de Expresiones Regulares (POSIX Extendido)

Introducción

Requisitos

Instalación

Configuración en tiempo de ejecución

Tipos de recursos

Constantes predefinidas

Ejemplos

Ver también

Table of Contents