Regex to replace html src attribute in PHP

Question

I'm trying to use regex to replace source attribute (could be image or any tag) in PHP.

I've a string like this:

$string2 = "<html><body><img src = 'images/test.jpg' /><img src = 'http://test.com/images/test3.jpg'/><video controls="controls" src='../videos/movie.ogg'></video></body></html>";

And I would like to turn it into:

$string2 = "<html><body><img src = 'test.jpg' /><img src = 'test3.jpg'/><video controls="controls" src='movie.ogg'></video></body></html>";

Heres what I tried :

$string2 = preg_replace("/src=["']([/])(.*)?["'] /", "'src=' . convert_url('$1') . ')'" , $string2);
echo htmlentities ($string2);

Basically it didn't change anything and gave me a warning about unescaped string.

Doesn't $1 send the content of the string ? What is wrong here ?

And the function of convert_url is from an example I posted here before :

function convert_url($url)
{
    if (preg_match('#^https?://#', $url)) {
        $url = parse_url($url, PHP_URL_PATH);
    }
    return basename($url);
}

It's supposed to strip out url paths and just return the filename.

the original string and what you want to turn it into are both empty strings -- is something missing? — ametren
– ametren, Commented May 18, 2012 at 19:04
You really shouldn't parse HTML with regex. You should find a pretty comprehensive answer as to why if you search SO. In the meantime, may I suggest DOM or SimpleXML — GordonM
– GordonM, Commented May 18, 2012 at 20:34
i mean try to replace in the regex all the " into \" but not the first and the last — Alexandre Khoury
– Alexandre Khoury, Commented May 19, 2012 at 4:02
possible duplicate of Grabbing the href attribute of an A element — Gordon
– Gordon, Commented May 23, 2012 at 6:08
Also, if you want to use regex and want to use a function in the replacement, you need preg_replace_callback. You cannot do convert_url('$1') like you do because that is evaluated before $1 exists. — Gordon
– Gordon, Commented May 23, 2012 at 6:12

Sampson · Accepted Answer · 2012-05-18 22:51:46Z

14

Don't use regular expressions on HTML - use the DOMDocument class.

$html = "<html>
           <body>
             <img src='images/test.jpg' />
             <img src='http://test.com/images/test3.jpg'/>
             <video controls='controls' src='../videos/movie.ogg'></video>
           </body>
         </html>";

$dom = new DOMDocument;  
libxml_use_internal_errors(true);

$dom->loadHTML( $html ); 
$xpath = new DOMXPath( $dom );
libxml_clear_errors();

$doc = $dom->getElementsByTagName("html")->item(0);
$src = $xpath->query(".//@src");

foreach ( $src as $s ) {
  $s->nodeValue = array_pop( explode( "/", $s->nodeValue ) );
}

$output = $dom->saveXML( $doc );

echo $output;

Which outputs the following:

<html>
  <body>
    <img src="test.jpg">
    <img src="test3.jpg">
    <video controls="controls" src="movie.ogg"></video>
  </body>
</html>

edited May 18, 2012 at 22:51

answered May 18, 2012 at 19:04

Sampson

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5 Comments

Ashesh Over a year ago

The dom document class is not very helpful if it is html embedded inside another HTML tag like <script></script> for e.g.

Sampson Over a year ago

@Ashesh I'm not I follow. You showed us PHP code - I'm showing you the solution.

Ashesh Over a year ago

Well I'm sorry I should have been more clear. Here's what I'm talking about: "<html><head><script>var html = '<img src = /images/test.jpg/>'</script></head><body></html>". In this case, the domdocument would not pickup on the image tag inside the javascript. That's why I need to use regex.

Sampson Over a year ago

@Ashesh The code above will work on the PHP string you have provided here. It converts the src elements to point only to the filename.

BasTaller Over a year ago

Sometimes it's not a good idea to load HTML parser. Especcialy on a short predefined text values (e.g. <img alt="smth" src="smwhr"/>), where only src="" and alt="" could vary.

ilanco · Accepted Answer · 2012-05-18 19:38:44Z

2

You have to use the e modifier.

$string = "<html><body><img src='images/test.jpg' /><img src='http://test.com/images/test3.jpg'/><video controls=\"controls\" src='../videos/movie.ogg'></video></body></html>";

$string2 = preg_replace("~src=[']([^']+)[']~e", '"src=\'" . convert_url("$1") . "\'"', $string);

Note that when using the e modifier, the replacement script fragment needs to be a string to prevent it from being interpreted before the call to preg_replace.

answered May 18, 2012 at 19:38

ilanco

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Comments

Abdo-Host · Accepted Answer · 2015-08-07 13:51:53Z

1

function replace_img_src($img_tag) {
    $doc = new DOMDocument();
    $doc->loadHTML($img_tag);
    $tags = $doc->getElementsByTagName('img');
    foreach ($tags as $tag) {
        $old_src = $tag->getAttribute('src');
        $new_src_url = 'website.com/assets/'.$old_src;
        $tag->setAttribute('src', $new_src_url);
    }
    return $doc->saveHTML();
}

answered Aug 7, 2015 at 13:51

Abdo-Host

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1 Comment

roghayeh hosseini Over a year ago

what is $img_tag ?

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