PHP RegEx remove empty paragraph tags

Question

I'm trying to remove all empty  tags CKEditor is inserting in to a description box but they all seem to vary. The possibilities seem to be:

<p></p>

<p>(WHITESPACE)</p>

<p>&nbsp;</p>

<p><br /></p>

<p>(NEWLINE)&nbsp;</p>

<p>(NEWLINE)<br /><br />(NEWLINE)&nbsp;</p>

With these possibilities, there could be any amount of whitespace,   and   tags in between the paragraphs, and there could be some of each kind in one paragraph.

I'm also not sure about the   tag, from what I've seen it could be  ,   or  .

I've searched SO for a similar answer but of all the answers I've seen they all seem to cater for just one of these cases, not all at once. I guess in simple terms what I'm asking is, Is there a regular expression I can use to remove all  tags from some HTML that don't have any alphanumeric text or symbols/punctuation in them?

Don't use regular expressions to parse HTML. You cannot reliably parse HTML with regular expressions. As soon as the HTML changes from your expectations, your code will be broken. See htmlparsing.com/php.html for examples of how to properly parse HTML with PHP modules. — Andy Lester
– Andy Lester, Commented Jan 10, 2013 at 15:14
So you really think I should use an HTML parser for a string such as 'Text ' - Seems like overkill don't you think? — Andy
– Andy, Commented Jan 10, 2013 at 15:17
This isn't parsing, techincally. And if the desired effect is suitably narrow (i.e. if you expect no understanding, just pattern matching), there's nothing wrong with Regexing a string. Cthulu will stay in his box. — FrankieTheKneeMan
– FrankieTheKneeMan, Commented Jan 10, 2013 at 15:18
I'm curious as to why @AndyLester thinks using DOMDocument to parse a 24 character HTML string is a good idea — Andy
– Andy, Commented Jan 10, 2013 at 15:23

Cerbrus · Accepted Answer · 2013-01-10 15:24:23Z

17

Well, in conflict with my suggestion not to parse HTML with regexes, I wrote up a regex to do just that:

"#<p>(\s|&nbsp;|</?\s?br\s?/?>)*</?p>#"

This will match properly for:

<p></p>

<p> </p> <!-- ([space]) -->

<p> </p> <!-- (That's a [tab] character in there -->

<p>&nbsp;</p>

<p><br /></p>

<p>
&nbsp;</p>

<p>
<br /><br />
&nbsp;</p>

What it does:

# /                --> Regex start
# <p>              --> match the opening <p> tag
# (                --> group open.
#   \s             --> match any whitespace character (newline, space, tab)
# |                --> or
#   &nbsp;         --> match &nbsp;
# |                --> or
#   </?\s?br\s?/?> --> match the <br> tag
# )*               --> group close, match any number of any of the elements in the group
# </?p>            --> match the closing </p> tag ("/" optional)
# /                --> regex end.

edited Jan 10, 2013 at 15:24

answered Jan 10, 2013 at 15:12

Cerbrus

73.3k19 gold badges138 silver badges151 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

FrankieTheKneeMan Over a year ago

Two things: use a different deilimiter, your regex will break like crazy because you forgot to escape the forwardslashes. Additionally, the examples in the post don't seem to have terminating tags. I wrote the regex slightly differently: #(\s+| |<br\s*/?>)*()(?=)# Of course, you can pepper in \s* for all sorts of whitespace concerns.

Cerbrus Over a year ago

@FrankieTheKneeMan: the examples in the posts seem to use  as terminating tags. I'll make the / in  optional.Other than that, thanks for the suggestions. I made such a "mess" of the   to catch all "possibilities" I've seen used.

Andy Over a year ago

Thanks a lot, it did't work with the / as the delimiter but worked perfectly once changed to #

Cerbrus Over a year ago

Ah, tagged php. Was used to the JS syntax, but somehow I forgot to escape the /'s in there -.- Thanks for accepting my answer!

Andy Over a year ago

@Cerbrus I forgot all about code blocks, how stupid of me. Cheers :)

|

Luis · Accepted Answer · 2015-05-06 12:34:26Z

5

The selected answer is great, but it doesn't work if  tag has inline style attributes defined, like .

A regex to match this, would be:

#<p[^>]*>(\s|&nbsp;|</?\s?br\s?/?>)*</?p>#

answered May 6, 2015 at 12:34

Luis

672 silver badges10 bronze badges

1 Comment

Andy Over a year ago

Good answer, I just tried this with all the test cases in my original question plus  and it works well

Collectives™ on Stack Overflow

PHP RegEx remove empty paragraph tags

2 Answers 2

6 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related