PHP preg_match_all(): Unknown modifier '>'

Question

I'm trying to create a Regex to filter out HTML opening tags in PHP

So far I came up with this pattern /\<[^/>]*\>/. This pattern seems to work on https://regexr.com/49vgk.

But as soon as I copy it into PHP I get this error: PHP preg_match_all(): Unknown modifier '>'

PHP Code:

$input = '<p>This is my HTML text that I want <b>all</b> opening tags from</p>';

$regexPattern = '/\<[^/>]*\>/';
$openingTags = preg_match_all($regexPattern, $input);

So far I'm unable to figure out what is causing this issue. Mostly because I've escaped most characters.

Does someone in the StackOverflow community know what I'm doing wrong and if so could explain me what it is I'm doing wrong?

Thanks in advance.

Welcome to Stack Overflow. Please realise that parsing HTML with regex is bad practice. The more you rely on it, the more it disappoints. — trincot, Mar 11 '19 at 13:25
As to your question, since you use `/` as regex delimiter, you must escape that character within the regex. Now PHP thinks your regex ends just before that first `>`. — trincot, Mar 11 '19 at 13:26

score 0 · Accepted Answer · edited Mar 11 '19 at 14:16

0

First of all, using regex to parse HTML is evil.

Now that this is out of the way, here is a working script:

$input = '<p>This is my HTML text that I want <b>all</b> opening tags from</p>';
$regexPattern = '/<[^\/][^>]*>/';
preg_match_all($regexPattern, $input, $matches);
print_r($matches[0]);

Array
(
    [0] => <p>
    [1] => <b>
)

Here is an explanation of the pattern <[^\/][^>]*>:

<      match an opening bracket
[^\/]  match a single character other than /
[^>]*  then match zero or more non closing bracket characters
>      match a closing bracket

As for your current errors, you have defined / to be a delimiter for the regex pattern. This means that if you want to use a literal forward slash, you therefore must escape it (as you would a regex metacharacter).

edited Mar 11 '19 at 14:16

E_net4

27,810
13
101
139

answered Mar 11 '19 at 13:27

Tim Biegeleisen

502,043
27
286
360

Thanks this helped, but I only wanted the opening tags, so I've changed the regex to `'/<[^\/>]*>/'` which seems to do exactly what I want. – jan swiebelt Mar 11 '19 at 13:32
User just wants to match opening tags therefor the pattern he has created is right. And, he just needs to escape '/' as he is using it to delimit the regex. – Parantap Parashar Mar 11 '19 at 13:32
@ParantapParashar Sorry, I have modified my answer per your comment. – Tim Biegeleisen Mar 11 '19 at 13:52
@TimBiegeleisen Thank you :) – Parantap Parashar Mar 11 '19 at 14:33

PHP preg_match_all(): Unknown modifier '>'

1 Answers1