I am using this regular expression to filter .pdffiles from the webpage:
$regex='|<a.*?href="(.*pdf?)"|';
It does the job if the link is like this:
www.xyz.com/trgrrtr/ghtty.pdf
but if the links are something like this, it is unable to filter:
www.xyz.com/trgrrtr/ghtty.pdf?code=KksRHhdVXAoECBFCVFpeXBsBUgYMDQpxd3J2d3F2fDtzfnFuLiErNXNpIG5kYm16aGhpcmxoa05QV1VKUVFFUxQ%3D
What regular expression I should use to filter out this link from a webpage?
First of all, you need to escape the ? otherwise it just makes the f in front of it optional. Then you could do something like this:
$regex = '|<a.*?href="([^"]*\.pdf\?[^"]*)"|';
The use of the negated character class makes sure that you cannot leave the attribute. (.* could consume the attribute-ending " as well, and go on until " matches another double quote further down the string.)
But I really recommend that you use a DOM parser to find the link-elements first. PHP has a built-in one and there is a very nice and convenient 3rd-party alternative.
The blog post An Improved Liberal, Accurate Regex Pattern for Matching URLs may help.
Related
I'm not familair with regular expressions. I'm trying to understand it, but it's difficult.
I've got a regular expression which will wrap any URL in an anchor tag. However, it's also wrapping URLs which are already in an anchor tag. I would like to prevent that, so I found a regular expression which does this for me.
?![^<]*</a>
However, I have no idea how I would add this to my existing regular expression. This is my current regular expression:
preg_replace('!(((ht)tp(s)?://)[-a-zA-Zа-яА-Я()0-9#:%_+.~#?&;//=]+)!i', '$1', $text); ?>
So, how can I skip an URL that is already wrapped in an anchor tag?
I'm gonna join the choir and say: Don't use regex for this - use a html parser.
This said - the regex you found isn't really a regex in itself. It's part of a negative look-ahead that kind of checks you aren't in an anchor. (It should really be (?![^<]*</a>).) It checks that following text up to the next < (or the end) isn't followed by </>.
Appending this to the en of your original RE will sometimes do the trick. I won't spend time thinking of situations it'll fail - but it probably will.
Along with some simplifications your regex should look like this:
(https?:\/\/[-\wа-яА-Я()#:%+.~#?&;\/=]+)(?![^<]*<\/a>)
This probably will work for you mostly, but probably will fail at times as well.
Regards
I need to use regex for a string to find matching results.
I need to find the (.+?) but would like to ignore everything where it says (*) right now:
$regex='#<span class="(*)">(.+?)</span>#';
Instead of ignoring (* ), it echoes out what is in (* ).
How can I ignore these and only get (.+?) ?
The parenthesizes mean capture: what's inside those () will be captured so you can use it later.
If you do not want something to be captured, because you don't want/need to use it later, just remove the parenthesizes.
I should add that using regular expressions to extract data from HTML is generally quite not such a good idea... You might want to use a DOM parser instead, with DOMDocument::loadHTML() for example .
I have written the following Regex in PHP for use within preg_replace().
/\b\S*(.com|.net|.us|.biz|.org|.info|.xxx|.mx|.ca|.fr|.in|.cn|.hk|.ng|.pr|.ph|.tv|.ru|.ly|.de|.my|.ir)\S*\b/i
This regex removes all URLs from a string pretty effectively this far (though I am sure I can write a better one). I need to be able to add an exclusion though from a specific domain. So the pseudo code will look like this:
IF string contains: .com or .net or. biz etc... and does not contain: foo.com THEN execute condition.
Any idea on how to do this?
Just add a negative lookahead assertion:
/(?<=\s|^)(?!\S*foo\.com)\S*\.(com|net|us|biz|org|info|xxx|mx|ca|fr|in|cn|hk|ng|pr|ph|tv|ru|ly|de|my|ir)\S*\b/im
Also, remember that you need to escape the dot - and that you can move it outside the alternation since each of the alternatives starts with a dot.
Use preg_replace_callback instead.
Let your callback decide whether to replace.
It can give more flexibility if the requirements become too complicated for a simple regex.
I'm trying to write a regular expression for matching the following HTML.
<span class="hidden_text">Some text here.</span>
I'm struggling to write out the condition to match it and have tried the following, but in some cases it selects everything after the span as well.
$condition = "/<span class=\"hidden_text\">(.*)<\/span>/";
If anyone could highlight what I'm doing wrong that would be great.
You need to use a non-greedy selection by adding ? after .* :
$condition = "/<span class=\"hidden_text\">(.*?)<\/span>/";
Note : If you need to match generic HTML, you should use a XML parser like DOM.
You shouldn’t try to use regular expressions on a non-regular language like HTML. Better use a proper HTML parser to parse the document.
See the following questions for further information on how to do that with PHP:
How to parse HTML with PHP?
Best methods to parse HTML
$condition = "/<span class=\"hidden_text\">(?<=^|>)[^><]+?(?=<|$)<\/span>/";
I got it. ;)
Chances are that you have multiple spans, and the regexp you're using will default to greedy mode
It's a lot easier using PHP's DOM Parser to extract content from HTML
I think this is what they call a teachable moment. :P Let us now compare and contrast the regex in your self-answer:
"/<span class=\"hidden_text\">(?<=^|>)[^><]+?(?=<|$)<\/span>/"
...and this one:
'~<span class="hidden_text">[^><]++</span>~'
PHP's double-quoted strings are subject to interpolation of embedded variables ($my_var) and evaluation of source code wrapped in braces ({return "foo"}). If you aren't using those features, it's best to use single-quoted strings to avoid surprises. As a bonus, you don't have to escape those double-quotes any more.
PHP allows you to use almost any ASCII punctuation character for the regex delimiters. By replacing your slashes with ~ I eliminated the need to escape the slash in the closing tag.
The lookbehind - (?<=^|>) - was not doing anything useful. It would only ever be evaluated immediately after the opening tag had been matched, so the previous character was always >.
[^><]+? is good (assuming you don't want to allow other tags in the content), but the quantifier doesn't need to be reluctant. [^><]+ can't possibly overrun the closing </span> tag, so there's point sneaking up on it. In fact, go ahead and kick the door in with a possessive quantifier: [^><]++.
Like the lookbehind before it, (?=<|$) was only taking up space. If [^><]+ consumes everything it can and the next character not <, you don't need a lookahead to tell you the match is going to fail.
Note that I'm just critiquing your regex, not fixing it; your regex and mine would probably yield the same results every time. There are many ways both of them can go wrong, even if the HTML you're working with is perfectly valid. Matching HTML with regexes is like trying to catch a greased pig.
in twitter
when you write #moustafa
will change to <a href='user/moustafa'>#moustafa</a>
now i want make the same thing
when write #moustafa + space its change #moustafa only
One regular expression that could be used (shamelessly stolen from the #anywhere javascript library mentioned in another answer) would be:
\B\#([a-zA-Z0-9_]{1,20})
This looks for a non–word-boundary (to prevent a#b [i.e. emails] from matching) followed by #, then between one and 20 (inclusive) characters in that character class. Of course, the anything-except-space route, as in other answers; it depends very much on what values are to be (dis)allowed in the label part of the #label.
To use the highlighted regex in PHP, something like the following could be used to replace a string $subject.
$subject = 'Hello, #moustafa how are you today?';
echo preg_replace('/\B\#([a-zA-Z0-9_]{1,20})/', '$0', $subject);
The above outputs something like:
Hello, #moustafa how are you today?
You're looking for a regular expression that matches #username, where username doesn't have a space? You can use:
#[^ ]+
If you know the allowed characters in a username you can be more specific, like if they have to be alphanumeric:
#[A-Za-z0-9]+
Regular Expressions in PHP are just Strings that start and end with the same character. By convention this character is /
So you can use something like this as an argument to any of the many php regular expression functions:
Not space:
"/[^ ]+/"
Alphanumeric only:
"/[A-Za-z0-9]+/"
Why not use the #anywhere javascript library that Twitter have recently released?
There are several libraries that perform this selection and linking for you. Currently I know of Java, Ruby, and PHP libraries under mzsanford's Github account: http://github.com/mzsanford/twitter-text-rb