I’ve been having issues with finding a solution to a regex conundrum I’m having.
Recently, I worked on a project where we needed to replace a list of words in a given text with a list of anchor tags.
For example, given a string
This is a test string
I may want to replace the word “test” with
<a target="_blank" href="https://website.com/string-random“>test</a>.
The resulting string should look like this
This is a <a target="_blank" href="https://website.com/string-random“>test</a> string
The replacement of the words is done in a loop
foreach ($documents as $document)
foreach ($links as $link)
replace keywords
What ends up happening in some scenarios is some of the urls in the anchor tags contain words that could potentially be replaced
For example, given this list of words to replace
[
{
'keyword': 'test',
'link': 'https://website.com/string-random'
},
{
'keyword': 'string',
'link': 'https://random.com/string'
}
]
After all the replacements are done, the sample string I gave above would look like this
This is a <a target="_blank" href="https://website.com/<a target="_blank" href="https://random.com/string“>string</a>-random“>test</a> <a target="_blank" href="https://random.com/string“>string</a>
Instead of
This is a <a target="_blank" href="https://website.com/string-random“>test</a> <a target="_blank" href="https://random.com/string“>string</a>
Currently, I am looking for a regular expression that would not match on any words surrounded by special characters as I think this would solve my problem.
Also very open to any other ideas on how to tackle this problem
This is not just about the previous replacements: any word that occurs within tag attributes / names / values is an issue.
In other words, you want to replace strings that are followed some chars where next < occurs before next > (strings between tags and not within tags)
Hence try this one :
(string-to-match)(?=[^>]*?<)
(replace string-to-match, obviously)
The other block is a lookahead : it ensures that you can read any char but >, as many times as needed, then a <
Try :
foreach ($wordlist as $word){
$document = preg_replace("~(?! )($word[keyword])(?! )~i","<a href='$word[link]'>$1<")
}
I found a pattern that works pretty well for me hear
$pattern = '/(?<!(>|\/|-))\b' . preg_quote($stringToReplace, '/') . '\b(?!(<|\/|-))/i';
Related
I have a forum that supports hashtags. I'm using the following line to convert all hashtags into links. I'm using the (^|\(|\s|>) pattern to avoid picking up named anchors in URLs.
$str=preg_replace("/(^|\(|\s|>)(#(\w+))/","$1$2",$str);
I'm using this line to pick up hashtags to store them in a separate field when the user posts their message, this picks up all hashtags EXCEPT those at the start of a new line.
preg_match_all("/(^|\(|\s|>)(#(\w+))/",$Content,$Matches);
Using the m & s modifiers doesn't make any difference. What am I doing wrong in the second instance?
Edit: the input text could be plain text or HTML. Example of problem input:
#startoftextreplacesandmatches #afterwhitespacereplacesandmatches <b>#insidehtmltagreplacesandmatches</b> :)
#startofnewlinereplacesbutdoesnotmatch :(
Your replace operation has a problem which you have evidently not yet come across - it will allow unescaped HTML special characters through. The reason I know this is because your regex allows hashtags to be prefixed with >, which is a special character.
For that reason, I recommend you use this code to do the replacement, which will double up as the code for extracting the tags to be inserted into the database:
$hashtags = array();
$expr = '/(?:(?:(^|[(>\s])#(\w+))|(?P<notag>.+?))/';
$str = preg_replace_callback($expr, function($matches) use (&$hashtags) {
if (!empty($matches['notag'])) {
// This takes care of HTML special characters outside hashtags
return htmlspecialchars($matches['notag']);
} else {
// Handle hashtags
$hashtags[] = $matches[2];
return htmlspecialchars($matches[1]).'#'.htmlspecialchars($matches[2]).'';
}
}, $str);
After the above code has been run, $str will contain the modified string, properly escaped for direct output, and $hashtags will be populated with all the tags matched.
See it working
I am trying to convert specific keywords in text, which are stored in array, to the links.
Example text:
$text='This text contains many keywords, but also formated keywords.'
So now I want to convert the word keywords to the #keywords.
I used the very simple preg_replace function
preg_replace('/keywords/i',' keywords ',$text);
but obviously it converts to link also the string already formatted as a link, so I get a messy html like:
$text='This text contains many keywords, but also formated keywords" title="keywords">keywords</a>.'
Expected result:
$text='This text contains many keywords, but also formated keywords.'
Any suggestions?
THX
EDIT
We are one step from the perfect function, but still not working well in this case:
$text='This text contains many keywords, but also formated
keywords.'
In this case it replaces also the word keywords in the href, so we again get the messy code like
keywords.com/keywords" title="keywords">keywords</a>
I'm not great with regular expressions, but maybe this one will work:
/[^#>"]keywords/i
What I think it will do is ignore any instances of #keywords, >keywords, and "keywords and find the rest.
EDIT:
After testing it out, it looks like that replaces the space before the word as well, and doesn't work if keywords is the beginning of the string. It also didn't preserve original capitalization. I have tested this one, and it works perfectly for me:
$string = "Keywords and keywords, plus some more keywords with the original keywords.";
$string = preg_replace("/(?<![#>\"])keywords/i", "$0", $string);
echo $string;
The first three are replaced, preserving the original capitalization, and the last one is left untouched. This one uses a negative lookbehind and backreferences.
EDIT 2:
OP edited question. With the new example provided, the following regex will work:
$string = 'This text contains many keywords, but also formated keywords.';
$string = preg_replace("/(?<![#>\".\/])keywords/i", "$0", $string);
echo $string;
// outputs: This text contains many keywords, but also formated keywords.
This will replace all instances of keywords that are not preceded by #, >, ", ., or /.
Here is the problem:
The keyword could be inside the href, the title, or the text of the link, and anywhere in there (like if the keyword was sanity and you already had href="insanity". Or even worse, you could have a non-keyword link that happens to contain a keyword, something like:
Click here to find more keywords and such!
In the above example, even though it fits every other possible criteria (it's got spaces before and after being the easiest one to test for), it still would result in a link within a link, which I think breaks the internet.
Because of this, you need to use lookaheads and lookbehinds to check if the keyword is wrapped in a link. But there is one catch: lookbehinds have to have a defined pattern (meaning no wild cards).
I thought I'd be the hero and show you the easy fix for your issue, which would be something to the effect of:
'/(?<!\<a.?>)[list|of|keywords](?!\<\/a>)/'
Except you can't do that because the lookbehind in this case has that wildcard. Without it, you end up with a super greedy expression.
So my proposed alternative is to use regex to find all link elements, then str_replace to swap them out with a placeholder, and then replacing them with the placeholder at the end.
Here's how I did it:
$text='This text contains many keywords, but also formated keywords.';
$keywords = array('text', 'formatted', 'keywords');
//This is just to make the regex easier
$keyword_list_pattern = '['. implode($keywords,"|") .']';
// First, get all matching keywords that are inside link elements
preg_match_all('/<a.*' . $keyword_list_pattern . '.*<\/a>/', $text, $links);
$links = array_unique($links[0]); // Cleaning up array for next step.
// Second, swap out all matches with a placeholder, and build restore array:
foreach($links as $count => $link) {
$link_key = "xxx_{$count}_xxx";
$restore_links[$link_key] = $link;
$text = str_replace($link, $link_key, $text);
}
// Third, we build a nice replacement array for the keywords:
foreach($keywords as $keyword) {
$keyword_links[$keyword] = "<a href='#$keyword'>$keyword</a>";
}
// Merge the restore links to the bottom of the keyword links for one mass replacement:
$keyword_links = array_merge($keyword_links, $restore_links);
$text = str_replace(array_keys($keyword_links), $keyword_links, $text);
echo $text;
You can change your RegEx so that it only targets keywords with a space in front. Since the formatted keywords do no contain a space. Here is an example.
$text = preg_replace('/ keywords/i',' keywords',$text);
I have some content that contains a token string in the form
$string_text = '[widget_abc]This is some text. This is some text, etc...';
And I want to pull all the text after the first ']' character
So the returned value I'm looking for in this example is:
This is some text. This is some text, etc...
preg_match("/^.+?\](.+)$/is" , $string_text, $match);
echo trim($match[1]);
Edit
As per author's request - added explanation:
preg_match(param1, param2, param3) is a function that allows you to match a single case scenario of a regular expression that you're looking for
param1 = "/^.+?](.+?)$/is"
"//" is what you put on the outside of your regular expression in param1
the i at the end represents case insensitive (it doesn't care if your letters are 'a' or 'A')
s - allows your script to go over multiple lines
^ - start the check from the beginning of the string
$ - go all the way to end of the string
. - represents any character
.+ - at least one or more characters of anything
.+? - at least one more more characters of anything until you reach
.+?] - at least one or more characters of anything until you reach ] (there is a backslash before ] because it represents something in regular expressions - look it up)
(.+)$ - capture everything after ] and store it as a seperate element in the array defined in param3
param2 = the string that you created.
I tried to simplify the explanations, I might be off, but I think I'm right for the most part.
The regex (?<=]).* will solve this problem if you can guarantee that there are no other square brackets on the line. In PHP the code will be:
if (preg_match('/(?<=\]).*/', $input, $group)) {
$match = $group[0];
}
This will transform [widget_abc]This is some text. This is some text, etc... into This is some text. This is some text, etc.... It matches everything that follows the ].
$output = preg_replace('/^[^\]]*\]/', '', $string_text);
Is there any particular reason why a regex is wanted here?
echo substr(strstr($string_text, ']'), 1);
A regex is definitely overkill for this instance.
Here is a nice one-liner :
list(, $result) = explode(']', $inputText, 2);
It does the job and is way less expensive than using regular expressions.
I'm having trouble using preg_match to find and replace a string. The string of interest is:
<span style="font-size:0.6em">EXPIRATION DATE: 04/30/2011</span>
I need to target and replace the date, "04/30/2011" with a different date. Can someone throw me a bone a give me the regular expression to match this pattern using preg_match in PHP? I also need it to match in such a way that it only replaces up to the first closing span and not closing span tags later in the code, e.g.:
<span style="font-size:0.6em">EXPIRATION DATE: 04/30/2011</span><span class="hello"></span>
I'm not versed in regex, and although I've spent the last hour trying to learn enough to make this work, I'm utterly failing. Thanks so much!
EDIT: As you can see this has gotten me exhausted. I did mean preg_replace, not preg_match.
If you're after a replacement, consider using preg_replace(), something like
preg_replace('#(\d{2})/(\d{2})/(\d{4})#', '<new date>', $string);
How about this:
$toBeFoundPattern = '/([0-9][0-9])\/([0-9][0-9])\/([0-9][0-9][0-9][0-9])/';
$toBeReplacedPattern = '$2.$1.$3';
$inString = '<span style="font-size:0.6em">EXPIRATION DATE: 04/30/2011</span>';
// Will convert from US date format 04/30/2011 to european format 30.04.2011
echo preg_replace( $toBeFoundPattern, $toBeReplacedPattern, $inString );
and prints
EXPIRATION DATE: 30.04.2011
Patterns always begin and end with identical so called delimiter characters. Often the character / is used.
$1 references the string, which matched the first string matched by ([0-9][0-9]), $2 references be (...) and $3 the four letters matched by the last (...).
[...] matched a single character, which is one of those listed inside the brackets. E.g. [a-z] matches all lower case letters.
To use the special meaning character / inside of a pattern, you need to escape it by \ to make it be the literal slash character.
Update: Using {..} as pointed out below is shorthand for repeated patterns.
Regex should be:
(0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)\d\d
If you want to only match one instance, this is OK. For multiple instances, use preg_match_all instead. Taken from http://www.regular-expressions.info/regexbuddy/datemmddyyyy.html.
Edit: are you looking to just search and replace inside a PHP script or do you want to do some javascript live replacement?
I´m using the following REGEXP:
$output = preg_replace( "/\/\/(.*)\\n/", "", $output );
The code works well BUT!!!!, when a URL like (http://this_is_not_a_comment.com/kickme), the code replaces it... (http://)
What can you do to no replace that URLs.
Thanks,
You need a regular expression that can distinguish between the code and the comments. In particular, since the sequence of // can either be in a string or a comment, you just need to distinguish between strings and comments.
Here’s an example that might do this:
/(?:([^\/"']+|\/\*(?:[^*]|\*+[^*\/])*\*+\/|"(?:[^"\\]|\\.)*"|'(?:[^'\\]|\\.)*')|\/\/.*)/
Using this in a replace function while replacing the matched string with the match of the first subpattern should then be able to remove the // style comments.
Some explanation:
[^/"']+ matches any character that is not the begin of a comment (both //… and /*…*/) or of a string
/\*(?:[^*]|\*+[^*/])*\*+/ matches the /* … */ style comments
"(?:[^"\\]|\\.)*" matches a string in double quotes
'(?:[^'\\]|\\.)*' matches a string in single quotes
\/\/.* finally matches the //… style comments.
As the first three constructs are grouped in a capturing group, the matched string is available and nothing is changed when replacing the matched string with the match of the first subpattern. Only if a //… style comment is matched the match of the first subpattern is empty and thus it’s replaced by an empty string.
But note that this may fail. I’m not quite sure if it works for any input.
$output = preg_replace( "/(?<!\:)\/\/(.*)\\n/", "", $output );