Explaination of how this ereg is used

rr1024

Thanks for any explainations you guys can provide:

ereg( "^{[^@} ]+@([a-zA-Z0-9-]+.)+([a-zA-Z0-9-]{2}|net|com|gov|mil|org|edu|int)\$",$address)

I'm trying to understand this in one of my files, it is of course for checking and email address.

Does this mean that it will take anything that is only 2 digits past the domain name i.e. domain extentions I guess it would be called?. and if it's three digits then it will only accept |net|com|gov|mil|org|edu|int any other three digits will be blocked...
It is an if ( ereg(....) )

laserlight

I'm more familiar with Perl compatible regex, but here's my take (which may be wrong, since I'm assuming from a PCRE background):

^
assert start of subject, i.e. match the pattern fully from the start of the subject

[^@ ]+
The [] indicates a character class. ^ negates the character class. As such, [^@] means to match characters other than '@'. The + means to match the preceding expression one or more times. So this expression means to match characters other than '@' one or more times.

@
This is straightforward, a literal '@' character.

([a-zA-Z0-9-]+.)+
Let's break this up further:
[a-zA-Z0-9-] is a character class consisting of case-insenstive alphanumeric characters and the dash '-', which is escaped and so is written as '-'. This character class is matches one or more times, since it is followed by a +.
. is a literal period '.'.

([a-zA-Z0-9-]{2}|net|com|gov|mil|org|edu|int)
Here {2} works like +, but matches exactly two times. The | means logical or.

\$
assert end of subject, i.e. match the pattern fully until the end of the subject

You could read the PHP Manual on regular expressions:
Regular Expression Functions (Perl-Compatible)
Regular Expression Functions (POSIX Extended)

John_McKean

I think this might cover your needs if not your question:

http://www.phpbuilder.com/board/showthread.php?t=10310013

toplay

The "\$" at the end of the expression shown is trying to literally match a dollar sign ($) at the end of the string. This will not work for an email address. Remove the backslash () just before the dollar sign in order for the dollar sign meta character to mean "assert end of subject".

There's no need to backslash the dash in the character class since it is at the end. This: [a-zA-Z0-9-] can be changed to be like this: [a-zA-Z0-9-] or this: [-a-zA-Z0-9]

There's lots of email expressions to pick from at:
http://www.regexlib.com/Search.aspx?k=email

🙂

Rodney_H_

Hi, there is a pretty good article of basic regex syntax and usage right here on phpbuilder: http://phpbuilder.com/columns/dario19990616.php3?aid=46

toplay

Yes, that's link # 8 under "Regex/PCRE" in my signature line.

Rodney_H_

toplay wrote:
Yes, that's link # 8 under "Regex/PCRE" in my signature line.

Gotcha, toplay. Apologies, and thanks. :o

laserlight

The "\$" at the end of the expression shown is trying to literally match a dollar sign ($) at the end of the string.

In this case, that's not true, unless POSIX differs in this regard to end of subject assertions. This regex pattern is a string delimited by double quotes, and recall that in such a string "\$" becomes a literal '$'. This means that the $ is actually not escaped in the regex, which is one reason why I find it better to delimit regex pattern strings by single quotes rather than by double quotes.

toplay

laserlight wrote:
In this case, that's not true, unless POSIX differs in this regard to end of subject assertions. This regex pattern is a string delimited by double quotes, and recall that in such a string "\$" becomes a literal '$'. This means that the $ is actually not escaped in the regex, which is one reason why I find it better to delimit regex pattern strings by single quotes rather than by double quotes.

I'm wrong. Yes, you are correct. I forgot about the double quotes thing.