Как найти ссылку в тексте php

Not regexp, but finds it all and makes sure that they are not already encompassed in a tag already. It also checks to make sure that the link isn’t encapsulated in (), [], «» or anything else with an open and close.

$txt = "Test text http://hello.world Test text 
http://google.com/file.jpg Test text https://hell.o.wor.ld/test?qwe=qwe Test text 
test text http://test.test/test <a href="http://example.com">I am already linked up</a>
It was also done in 1927 (http://test.com/reference) Also check this out:http://test/index&t=27";
$holder = explode("http",$txt);
for($i = 1; $i < (count($holder));$i++) {
    if (substr($holder[$i-1],-6) != 'href="') { // this means that the link is not alread in an a tag.
        if (strpos($holder[$i]," ")!==false) //if the link is not the last item in the text block, stop at the first space
            $href = substr($holder[$i],0,strpos($holder[$i]," "));
        else                                //else it is the last item, take it
            $href = $holder[$i];
        if (ctype_punct(substr($holder[$i-1],strlen($holder[$i-1])-1)) && ctype_punct(substr($holder[$i],strlen($holder[$i])-1)))
            $href = substr($href,0,-1);     //if both the fron and back of the link are encapsulated in punctuation, truncate the link by one
        $holder[$i] = implode("$href" target="_blank" class="link">http$href</a>",explode($href,$holder[$i]));
        $holder[$i-1] .= "<a href="";
    }
}
$txt = implode("http",$holder);

echo $txt;

Output:

Test text <a href="http://hello.world" target="_blank" class="link">http://hello.world</a> Test text 
<a href="http://google.com/file.jpg" target="_blank" class="link">http://google.com/file.jpg</a> Test text <a href="https://hell.o.wor.ld/test?qwe=qwe" target="_blank" class="link">https://hell.o.wor.ld/test?qwe=qwe</a> Test text 
test text <a href="http://test.test/test" target="_blank" class="link">http://test.test/test</a> <a href="http://example.com">I am already linked up</a>
It was also done in 1927 (<a href="http://test.com/reference" target="_blank" class="link">http://test.com/reference</a>) Also check this out:<a href="http://test/index&amp;t=27" target="_blank" class="link">http://test/index&amp;t=27</a>

Копирование материалов разрешается только с указанием автора (Михаил Русаков) и индексируемой прямой ссылкой на сайт (http://myrusakov.ru)!

Если у Вас остались какие-либо вопросы, либо у Вас есть желание высказаться по поводу этой статьи, то Вы можете оставить свой комментарий внизу страницы.

Если Вам понравился сайт, то разместите ссылку на него (у себя на сайте, на форуме, в контакте):

1. Кнопка:

   Она выглядит вот так:

2. Текстовая ссылка:

   Она выглядит вот так: Как создать свой сайт

3. BB-код ссылки для форумов (например, можете поставить её в подписи):
   

From blogging to log analysis and search engine optimisation (SEO)
people are looking for scripts that can parse web pages and RSS feeds
from other websites — to see where their traffic is coming from among
other things.

Parsing your own HTML should be no problem —
assuming that you use consistent formatting — but once you set your
sights at parsing other people’s HTML the frustration really sets in.
This page presents some regular expressions and a commentary that will
hopefully point you in the right direction.

Simplest Case

Let’s start with the simplest case — a well formatted link with no
extra attributes:

/<a href="([^"]*)">(.*)</a>/iU

This, believe it or not, is a very simple regular expression (or
«regexp» for short). It can be broken down as follows:

• starts with: <a href=»
• a series of characters up to, but not including, the next double-quote («) — 1st capture
• the string: «>
• a series of any characters — 2nd capture
• ends with: </a>

We’re also using two ‘pattern modifiers’:

• i — matches are ‘caseless’ (upper or lower case doesn’t matter)
• U — matches are ‘ungreedy’

The first modifier means that we’re matching <A> as well as
<a>. The ‘ungreedy’ modifier is necessary because otherwise the
second captured string could (by being ‘greedy’) extend from the
contents of one link all the way to the end of another link.

One shortcoming of this regexp is that it won’t match link tags that
include a line break — fortunately there’s a modifer for this as
well:

/<ashref="([^"]*)">(.*)</a>/siU

Now the ‘.’ character will match any character
including line breaks. We’ve also changed the first
space to a ‘whitespace’ character type so that it can match a space, tab
or line break. It’s necessary to have some kind of whitespace in that
position so we don’t match other tags such as <area>.

For more information on pattern modifiers see the link at the bottom
of this page.

Room for Extra Attributes

Most link tags contain a lot more than just an href
attribute. Other common attributes include: rel, target and title.
They can appear before or after the href attribute:

/<as[^>]*href="([^"]*)"[^>]*>(.*)</a>/siU

We’ve added extra patterns before and after the href attribute. They
will match any series of characters NOT containing the >
symbol. It’s always better when writing regular expressions to specify
exactly which characters are allowed and not allowed —
0rather that using the wildcard (‘.’) character.

Allow for Missing Quotes

Up to now we’ve assumed that the link address is going to be enclosed
in double-quotes. Unfortunately there’s nothing enforcing this so a lot
of people simply leave them out. The problem is that we were relying on
the quotes to be there to indicate where the address starts and
ends. Without the quotes we have a problem.

It would be simple enough (even trivial) to write a second regexp,
but where’s the fun in that when we can do it all with one:

/<as[^>]*href=("??)([^" >]*?)\1[^>]*>(.*)</a>/siU

What can I say? Regular expressions are a lot of fun to work with
but when it takes a half-hour to work out where to put an extra
? your really know you’re in deep.

Firstly, what’s with those extra ?’s?

Because we used the U modifier, all patterns in the regexp
default to ‘ungreedy’. Adding an extra ? after a ? or
* reverses that behaviour back to ‘greedy’ but just for the
preceding pattern. Without this, for reasons that are difficult to
explain, the expression fails. Basically anything following
href= is lumped into the [^>]* expression.

We’ve added an extra capture to the regexp that matches a
double-quote if it’s there: («??). There is then a
backreference \1 that matches the closing double-quote — if
there was an opening one.

To cater for links without quotes, the pattern to match the link
address itself has been changed from [^»]* to [^»
>]*?. That means that the link can be terminated by not just a
double-quote (the previous behaviour) but also a space or >
symbol.

This means that links with addresses containing unescaped spaces will no longer be
captured!

Refining the Regexp

Given the nature of the WWW there are always going to be cases where
the regular expression breaks down. Small changes to the patterns can
fix these.

spaces around the = after href:

/<as[^>]*hrefs*=s*("??)([^" >]*?)\1[^>]*>(.*)</a>/siU

matching only links starting with http:

/<as[^>]*href=("??)(http[^" >]*?)\1[^>]*>(.*)</a>/siU

single quotes around the link address:

/<as[^>]*href=(["']??)([^" >]*?)\1[^>]*>(.*)</a>/siU

And yes, all of these modifications can be used at the same time to
make one super-regexp, but the result is just too painful to look at so
I’ll leave that as an exercise.

Note: All of the expressions on this page have been
tested to some extent, but mistakes can occur in transcribing so please
report any errors you may have found when implementing these
examples.

Using the Regular Expression to parse HTML

Using the default for preg_match_all the array returned contains an array
of the first ‘capture’ then an array of the second capture and so
forth. By capture we mean patterns contained in ():

<?PHP
// Original PHP code by Chirp Internet: www.chirpinternet.eu
// Please acknowledge use of this code by including this header.

$url = "http://www.example.net/somepage.html";
$input = @file_get_contents($url) or die("Could not access file: $url");
$regexp = "<as[^>]*href=("??)([^" >]*?)\1[^>]*>(.*)</a>";
if(preg_match_all("/$regexp/siU", $input, $matches)) {
// $matches[2] = array of link addresses
// $matches[3] = array of link text - including HTML code
}
?>

Using PREG_SET_ORDER each link matched has it’s own array in
the return value:

<?PHP
// Original PHP code by Chirp Internet: www.chirpinternet.eu
// Please acknowledge use of this code by including this header.

$url = "http://www.example.net/somepage.html";
$input = @file_get_contents($url) or die("Could not access file: $url");
$regexp = "<as[^>]*href=("??)([^" >]*?)\1[^>]*>(.*)</a>";
if(preg_match_all("/$regexp/siU", $input, $matches, PREG_SET_ORDER)) {
foreach($matches as $match) {
// $match[2] = link address
// $match[3] = link text
}
}
?>

If you find any cases where this code falls down, let us know using
the Feedback link below.

Before using this or similar scripts to fetch pages from other
websites, we suggest you read through the related article on setting a user agent and parsing robots.txt.

First checking robots.txt

As mentioned above, before using a script to download files you
should always check the robots.txt
file. Here we’re making use of the robots_allowed function
from the article linked above to determine whether we’re allowed to
access files:

<?PHP
// Original PHP code by Chirp Internet: www.chirpinternet.eu
// Please acknowledge use of this code by including this header.

$url = "http://www.example.net/somepage.html";
if(robots_allowed($url, "NameOfAgent")) {
$input = @file_get_contents($url) or die("Could not access file: $url");
$regexp = "<as[^>]*href=("??)([^" >]*?)\1[^>]*>(.*)</a>";
if(preg_match_all("/$regexp/siU", $input, $matches, PREG_SET_ORDER)) {
foreach($matches as $match) {
// $match[2] = link address
// $match[3] = link text
}
}
} else {
die('Access denied by robots.txt');
}
?>

Now you’re well on the way to building a professional web spider. If
you’re going to use this in practice you might want to look at: caching
the robots.txt file so that it’s not downloaded every time (a la Slurp);
checking the server headers and server
response codes; and adding a pause between multiple requests — for
starters.

Translations

• French

References

• PHP.net: PCRE: Pattern Modifiers

• PHP Parsing HTML to find Links
• PHP Parsing HTML files with DOMDocument and DOMXpath
• PHP Parsing robots.txt
• PHP Listing files in a ZIP archive

< PHP

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