I would like to get the urls from a webpage that starts with "../category/" from these tags below:
PC<br>
Carpet<br>
Any suggestion would be very much appreciated.
Thanks!
No regular expressions is required. A simple XPath query with DOM will suffice:
$dom = new DOMDocument;
$dom->loadHTML($html);
$xpath = new DOMXPath($dom);
$nodes = $xpath->query('//a[starts-with(#href, "../category/")]');
foreach ($nodes as $node) {
echo $node->nodeValue.' = '.$node->getAttribute('href').PHP_EOL;
}
Will print:
PC = ../category/product/pc.html
Carpet = ../category/product/carpet.html
This regex searches for your ../category/ string:
preg_match_all('#......="(\.\./category/.*?)"#', $test, $matches);
All text literals are used for matching. You can replace the ..... to make it more specific. Only the \. need escaping. The .*? looks for a variable length string. And () captures the matched path name, so it appears in $matches. The manual explains the rest of the syntax. http://www.php.net/manual/en/book.pcre.php
Related
I have the following regex to find anchor tag that has 'Kontakt' as the anchor text:
#<a.*href="[^"]*".*>Kontakt<\/a>#
Here is the string to find from:
<li class="item-133">Wissenswertes</li><li class="item-115"><a href="/team" >Team</li><li class="item-116 menu-parent"></span></li><li class="item-350"><a href="/kontakt" >Kontakt</li></ul>
So the result should be:
<a href="/kontakt" >Kontakt</a>
But the result I get is:
Wissenswertes</li><li class="item-115"><a href="/team" >Team</li><li class="item-116 menu-parent"></span></li><li class="item-350"><a href="/kontakt" >Kontakt
And here is my PHP code:
$pattern = '#<a.*href="[^"]*".*>Kontakt<\/a>#';
preg_match_all($pattern, $string, $matches);
You are using preg_match_all() so I assume you are willing to receive multiple qualifying anchor tags. Parsing valid HTML with a legitimate DOM parser will always be more stable and easier to read than the equivalent regex technique. It's just not a good idea to rely on regex for DOM parsing because regex is "DOM-unaware" -- it just matches things that look like HTML entities.
In the XPath query, search for <a> tags (existing at any depth in the document) which have the qualifying string as the whole text.
Code: (Demo)
$html = <<<HTML
<li class="item-133">Wissenswertes</li><li class="item-115"><a href="/team" >Team</li><li class="item-116 menu-parent"></span></li><li class="item-350"><a href="/kontakt" >Kontakt</li></ul>
HTML;
$dom = new DOMDocument;
libxml_use_internal_errors(true);
$dom->loadHTML($html);
$xpath = new DOMXPath($dom);
$result = [];
foreach ($xpath->query('//a[text() = "Kontakt"]') as $a) {
$result[] = $dom->saveHtml($a);
}
var_export($result);
Output:
array (
0 => 'Kontakt',
)
Is it more concise to use regex? Yes, but it is also less reliable for general use.
You will notice that the DOMDocument also automatically cleans up the unnecessary spacing in your markup.
If you can trust your input will always have <a href in every anchor tag then try:
'#<a href="[^"]*"[^>]*>Kontakt<\/a>#';
// Instead of what you have:
'#<a.*href="[^"]*".*>Kontakt<\/a>/#';
.* is the "wildcard" meta-character . and the "zero or more times" quantifier * together.
.* matches anything any number of times.
Try it https://regex101.com/r/qxnRZv/1
Your regex:
...a.*href...
is greedy, which means: "after a, match as many characters as possible before a href". That causes your regex to return multiple hrefs.
You can use the lazy-mode operator ? :
...a.*?href....
which means "after a, match as few characters as possible before a href". It should work.
Iam making a webcrawler and I need to extract the metadata that contains the description, this is what I did:
$html = file_get_contents('http://www.google.com');
preg_match('/<meta name="description" content="(.*)"/>\i', $html, $description);
$description_out = $description;
var_dump($description_out);
and I get this error
Warning: preg_match(): Unknown modifier '>' in
C:\xampp\htdocs\webcrawler\php-web-crawler\index.php on line 21
What is the correct regular expression?
Your pattern is incorrect. You start with a / delimiter and then you have an unescaped / in the pattern this ends the pattern and everything after it is read as modifiers.
Then your end delimiter was on the wrong way, was \ should be /.
'/<meta name="description" content="(.*)"\/>/i',
As an alternative, instead of using a regex you might use DOMDocument and DOMXPath with an xpath expression /html/head/meta[#name="description"]/#content to get the content attribute.
$document = new DOMDocument();
$document->loadHTML($html);
$xpath = new DOMXPath($document);
$items = $xpath->query('/html/head/meta[#name="description"]/#content');
foreach ($items as $item) {
echo $item->value . "<br>";
}
The $items are of type DOMNodeList which you could loop using for example a foreach. The $item is of type DOMAttr from which you can get the value.
I would like to get back the number which is between span HTML tags. The number may change!
<span class="topic-count">
::before
"
24
"
::after
</span>
I've tried the following code:
preg_match_all("#<span class=\"topic-count\">(.*?)</span>#", $source, $nombre[$i]);
But it doesn't work.
Entire code:
$result=array();
$page = 201;
while ($page>=1) {
$source = file_get_contents ("http://www.jeuxvideo.com/forums/0-27047-0-1-0-".$page."-0-counter-strike-global-offensive.htm");
preg_match_all("#<span class=\"topic-count\">(.*?)</span>#", $source, $nombre[$i]);
$result = array_merge($result, $nombre[$i][1]);
print("Page : ".$page ."\n");
$page-=25;
}
print_r ($nombre);
Can do with
preg_match_all(
'#<span class="topic-count">[^\d]*(\d+)[^\d]*?</span>#s',
$html,
$matches
);
which would capture any digits before the end of the span.
However, note that this regex will only work for exactly this piece of html. If there is a slight variation in the markup, for instance, another class or another attribute, the pattern will not work anymore. Writing reliable regexes for HTML is hard.
Hence the recommendation to use a DOM parser instead, e.g.
libxml_use_internal_errors(true);
$dom = new DOMDocument;
$dom->loadHTMLFile('http://www.jeuxvideo.com/forums/0-27047-0-1-0-1-0-counter-strike-global-offensive.htm');
libxml_use_internal_errors(false);
$xpath = new DOMXPath($dom);
foreach ($xpath->evaluate('//span[contains(#class, "topic-count")]') as $node) {
if (preg_match_all('#\d+#s', $node->nodeValue, $topics)) {
echo $topics[0][0], PHP_EOL;
}
}
DOM will parse the entire page into a tree of nodes, which you can then query conveniently via XPath. Note the expression
//span[contains(#class, "topic-count")]
which will give you all the span elements with a class attribute containing the string topic-count. Then if any of these nodes contain a digit, echo it.
The following situation:
$text = "This is some <span class='classname'>example</span> text i'm writing to
demonstrate the <span class='classname otherclass'>problem</span> of this.<br />";
preg_match_all("|<[^>/]*(classname)(.+)>(.*)</[^>]+>|U", $text, $matches, PREG_PATTERN_ORDER);
I need an array ($matches) where in one field is "<span class='classname'>example</span>" and in another "example".
But what i get here is one field with "<span class='classname'>example</span>" and one with "classname".
It also should contain the values for the other matches, of course.
how can i get the right values?
You would be better off with a DOM parser, however this question is more to do with how capturing works in Regexes in general.
The reason you are getting classname as a match is because you are capturing it by putting () around it. They are completely unnecessary so you can just remove them. Similarly, you don't need them around .+ since you don't want to capture that.
If you had some group that you had to enclose in () as grouping rather than capturing, start the group with ?: and it won't be captured.
The safe/easy way:
$text = 'blah blah blah';
$dom = new DOM();
$dom->loadHTML($text);
$xp = new DOMXPath($dom);
$nodes = $xp->query("//span[#class='classname']");
foreach($nodes as $node) {
$innertext = $node->nodeValue;
$html = // see http://stackoverflow.com/questions/2087103/innerhtml-in-phps-domdocument
}
I need to convert
$text = 'We had <i>fun</i>. Look at this photo of Joe';
[Edit] There could be multiple links in the text.
to
$text = 'We had fun. Look at this photo (http://example.com) of Joe';
All HTML tags are to be removed and the href value from <a> tags needs to be added like above.
What would be an efficient way to solve this with regex? Any code snippet would be great.
First do a preg_replace to keep the link. You could use:
preg_replace('(.*?)', '$\2 ($\1)', $str);
Then use strip_tags which will finish off the rest of the tags.
try an xml parser to replace any tag with it's inner html and the a tags with its href attribute.
http://www.php.net/manual/en/book.domxml.php
The DOM solution:
$dom = new DOMDocument;
$dom->loadHTML($html);
$xpath = new DOMXPath($dom);
foreach($xpath->query('//a[#href]') as $node) {
$textNode = new DOMText(sprintf('%s (%s)',
$node->nodeValue, $node->getAttribute('href')));
$node->parentNode->replaceChild($textNode, $node);
}
echo strip_tags($dom->saveHTML());
and the same without XPath:
$dom = new DOMDocument;
$dom->loadHTML($html);
foreach($dom->getElementsByTagName('a') as $node) {
if($node->hasAttribute('href')) {
$textNode = new DOMText(sprintf('%s (%s)',
$node->nodeValue, $node->getAttribute('href')));
$node->parentNode->replaceChild($textNode, $node);
}
}
echo strip_tags($dom->saveHTML());
All it does is load any HTML into a DomDocument instance. In the first case it uses an XPath expression, which is kinda like SQL for XML, and gets all links with an href attribute. It then creates a text node element from the innerHTML and the href attribute and replaces the link. The second version just uses the DOM API and no Xpath.
Yes, it's a few lines more than Regex but this is clean and easy to understand and it won't give you any headaches when you need to add additional logic.
I've done things like this using variations of substring and replace. I'd probably use regex today but you wanted an alternative so:
For the <i> tags, I'd do something like:
$text = replace($text, "<i>", "");
$text = replace($text, "</i>", "");
(My php is really rusty, so replace may not be the right function name -- but the idea is what I'm sharing.)
The <a> tag is a bit more tricky. But, it can be done. You need to find the point that <a starts and that the > ends with. Then you extract the entire length and replace the closing </a>
That might go something like:
$start = strrpos( $text, "<a" );
$end = strrpos( $text, "</a>", $start );
$text = substr( $text, $start, $end );
$text = replace($text, "</a>", "");
(I don't know if this will work, again the idea is what I want to communicate. I hope the code fragments help but they probably don't work "out of the box". There are also a lot of possible bugs in the code snippets depending on your exact implementation and environment)
Reference:
strrpos - http://www.php.net/manual/en/function.strrpos.php
replace - http://www.php.net/manual/en/function.str-replace.php
substr - http://php.net/manual/en/function.substr.php
It's also very easy to do with a parser:
# available from http://simplehtmldom.sourceforge.net
include('simple_html_dom.php');
# parse and echo
$html = str_get_html('We had <i>fun</i>. Look at this photo of Joe');
$a = $html->find('a');
$a[0]->outertext = "{$a[0]->innertext} ( {$a[0]->href} )";
echo strip_tags($html);
And that produces the code you want in your test case.