Strip all HTML attributes except for src_问答_开发者

I'm trying to remove all tag attributes except for the src attribute. For example:

<p id="paragraph" class="green">This is a paragraph with an image <img src="/path/to/image.jpg" width="50" height="75"/></p>

Would be returned as:

<p>This is a paragraph with an image <img src="/path/to/image.jpg" /></p>

I have a regula开发者_JAVA技巧r expression to strip all attributes, but I'm trying to tweak it to leave in src. Here's what I have so far:

<?php preg_replace('/<([A-Z][A-Z0-9]*)(\b[^>]*)>/i', '<$1>', '<html><goes><here>');

This might work for your needs:

$text = '<p id="paragraph" class="green">This is a paragraph with an image <img src="/path/to/image.jpg" width="50" height="75"/></p>';

echo preg_replace("/<([a-z][a-z0-9]*)(?:[^>]*(\ssrc=['\"][^'\"]*['\"]))?[^>]*?(\/?)>/i",'<$1$2$3>', $text);

// <p>This is a paragraph with an image <img src="/path/to/image.jpg"/></p>

The RegExp broken down:

/              # Start Pattern
 <             # Match '<' at beginning of tags
 (             # Start Capture Group $1 - Tag Name
  [a-z]         # Match 'a' through 'z'
  [a-z0-9]*     # Match 'a' through 'z' or '0' through '9' zero or more times
 )             # End Capture Group
 (?:           # Start Non-Capture Group
  [^>]*         # Match anything other than '>', Zero or More Times
  (             # Start Capture Group $2 - ' src="...."'
   \s            # Match one whitespace
   src=          # Match 'src='
   ['"]          # Match ' or "
   [^'"]*        # Match anything other than ' or " 
   ['"]          # Match ' or "
  )             # End Capture Group 2
 )?            # End Non-Capture Group, match group zero or one time
 [^>]*?        # Match anything other than '>', Zero or More times, not-greedy (wont eat the /)
 (\/?)         # Capture Group $3 - '/' if it is there
 >             # Match '>'
/i            # End Pattern - Case Insensitive

Add some quoting, and use the replacement text <$1$2$3> it should strip any non src= properties from well-formed HTML tags.

Please Note This isn't necessarily going to work on ALL input, as the Anti-HTML + RegExp people are so cleverly noting below. There are a few fallbacks, most notably <p style=">"> would end up <p>"> and a few other broken issues... I would recommend looking at Zend_Filter_StripTags as a full proof tags/attributes filter in PHP

You usually should not parse HTML using regular expressions.

Instead, you should call DOMDocument::loadHTML.
You can then recurse through the elements in the document and call removeAttribute.

Alright, here's what I used that seems to be working well:

<([A-Z][A-Z0-9]*)(\b[^>src]*)(src\=[\'|"|\s]?[^\'][^"][^\s]*[\'|"|\s]?)?(\b[^>]*)>

Feel free to poke any holes in it.

Unfortunately I'm not sure how to answer this question for PHP. If I were using Perl I would do the following:

use strict;
my $data = q^<p id="paragraph" class="green">This is a paragraph with an image <img src="/path/to/image.jpg" width="50" height="75"/></p>^;

$data =~ s{
    <([^/> ]+)([^>]+)> # split into tagtype, attribs
}{
    my $attribs = $2;
    my @parts = split( /\s+/, $attribs ); # separate by whitespace
    @parts = grep { m/^src=/i } @parts;   # retain just src tags
    if ( @parts ) {
        "<" . join( " ", $1, @parts ) . ">";
    } else {
        "<" . $1 . ">";
    }
}xseg;

print( $data );

which returns

<p>This is a paragraph with an image <img src="/path/to/image.jpg"></p>

Do not use regex to parse valid html. Use regex to parse an html document ONLY if all available DOM parsers are failing you. I super-love regex, but regex is "DOM-ignorant" and it will quietly fail and/or mutate your document.

I generally prefer a mix of DOMDocument and XPath to concisely, directly, and intuitively target document entities.

With only a couple of minor exceptions, the XPath expression closely resembles its logic in plain English.

//@*[not(name()="src")]

at any level in the document (//)
find any attribute (@*)
satisfying these requirements ([])
that is not (not())
named "src" (name()="src")

This is far more readable, attractive, ad maintainable.

Code: (Demo)

$html = <<<HTML
<p id="paragraph" class="green">
    This is a paragraph with an image <img src="/path/to/image.jpg" width="50" height="75"/>
</p>
HTML;

$dom = new DOMDocument;
$dom->loadHTML($html, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
$xpath = new DOMXPath($dom);
foreach ($xpath->query('//@*[not(name()="src")]') as $attr) {
    $attr->parentNode->removeAttribute($attr->nodeName);
}
echo $dom->saveHTML();

Output:

<p>
    This is a paragraph with an image <img src="/path/to/image.jpg">
</p>

If you want to add another exempt attribute, you can use or

//@*[not(name()="src" or name()="href")]

As above introduced you shouldn use regex to parse html, or xml.

I would do your example with str_replace(); if its all time the same.

$str = '<p id="paragraph" class="green">This is a paragraph with an image <img src="/path/to/image.jpg" width="50" height="75"/></p>';

$str = str_replace('id="paragraph" class="green"', "", $str);

$str = str_replace('width="50" height="75"',"",$str);