How to extract img src, title and alt from html using php?

https://stackoverflow.com/questions/138313

02-07-2019
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Question

I would like to create a page where all images which reside on my website are listed with title and alternative representation.

I already wrote me a little program to find and load all HTML files, but now I am stuck at how to extract src, title and alt from this HTML:

<img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny" />

I guess this should be done with some regex, but since the order of the tags may vary, and I need all of them, I don't really know how to parse this in an elegant way (I could do it the hard char by char way, but that's painful).

Solution

EDIT : now that I know better

Using regexp to solve this kind of problem is a bad idea and will likely lead in unmaintainable and unreliable code. Better use an HTML parser.

Solution With regexp

In that case it's better to split the process into two parts :

get all the img tag
extract their metadata

I will assume your doc is not xHTML strict so you can't use an XML parser. E.G. with this web page source code :

/* preg_match_all match the regexp in all the $html string and output everything as 
an array in $result. "i" option is used to make it case insensitive */

preg_match_all('/<img[^>]+>/i',$html, $result); 

print_r($result);
Array
(
    [0] => Array
        (
            [0] => <img src="/Content/Img/stackoverflow-logo-250.png" width="250" height="70" alt="logo link to homepage" />
            [1] => <img class="vote-up" src="/content/img/vote-arrow-up.png" alt="vote up" title="This was helpful (click again to undo)" />
            [2] => <img class="vote-down" src="/content/img/vote-arrow-down.png" alt="vote down" title="This was not helpful (click again to undo)" />
            [3] => <img src="http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG" height=32 width=32 alt="gravatar image" />
            [4] => <img class="vote-up" src="/content/img/vote-arrow-up.png" alt="vote up" title="This was helpful (click again to undo)" />

[...]
        )

)

Then we get all the img tag attributes with a loop :

Regexps are CPU intensive so you may want to cache this page. If you have no cache system, you can tweak your own by using ob_start and loading / saving from a text file.

How does this stuff work ?

First, we use preg_ match_ all, a function that gets every string matching the pattern and ouput it in it's third parameter.

The regexps :

<img[^>]+>

We apply it on all html web pages. It can be read as every string that starts with "<img", contains non ">" char and ends with a >.

(alt|title|src)=("[^"]*")

We apply it successively on each img tag. It can be read as every string starting with "alt", "title" or "src", then a "=", then a ' " ', a bunch of stuff that are not ' " ' and ends with a ' " '. Isolate the sub-strings between ().

Finally, every time you want to deal with regexps, it handy to have good tools to quickly test them. Check this online regexp tester.

EDIT : answer to the first comment.

It's true that I did not think about the (hopefully few) people using single quotes.

Well, if you use only ', just replace all the " by '.

If you mix both. First you should slap yourself :-), then try to use ("|') instead or " and [^ø] to replace [^"].

OTHER TIPS

$url="http://example.com";

$html = file_get_contents($url);

$doc = new DOMDocument();
@$doc->loadHTML($html);

$tags = $doc->getElementsByTagName('img');

foreach ($tags as $tag) {
       echo $tag->getAttribute('src');
}

Just to give a small example of using PHP's XML functionality for the task:

$doc=new DOMDocument();
$doc->loadHTML("<html><body>Test<br><img src=\"myimage.jpg\" title=\"title\" alt=\"alt\"></body></html>");
$xml=simplexml_import_dom($doc); // just to make xpath more simple
$images=$xml->xpath('//img');
foreach ($images as $img) {
    echo $img['src'] . ' ' . $img['alt'] . ' ' . $img['title'];
}

I did use the DOMDocument::loadHTML() method because this method can cope with HTML-syntax and does not force the input document to be XHTML. Strictly speaking the conversion to a SimpleXMLElement is not necessary - it just makes using xpath and the xpath results more simple.

If it's XHTML, your example is, you need only simpleXML.

<?php
$input = '<img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny"/>';
$sx = simplexml_load_string($input);
var_dump($sx);
?>

Output:

object(SimpleXMLElement)#1 (1) {
  ["@attributes"]=>
  array(3) {
    ["src"]=>
    string(22) "/image/fluffybunny.jpg"
    ["title"]=>
    string(16) "Harvey the bunny"
    ["alt"]=>
    string(26) "a cute little fluffy bunny"
  }
}

The script must be edited like this

foreach( $result[0] as $img_tag)

because preg_match_all return array of arrays

You may use simplehtmldom. Most of the jQuery selectors are supported in simplehtmldom. An example is given below

// Create DOM from URL or file
$html = file_get_html('http://www.google.com/');

// Find all images
foreach($html->find('img') as $element)
       echo $element->src . '<br>';

// Find all links
foreach($html->find('a') as $element)
       echo $element->href . '<br>';

I used preg_match to do it.

In my case, I had a string containing exactly one <img> tag (and no other markup) that I got from Wordpress and I was trying to get the src attribute so I could run it through timthumb.

// get the featured image
$image = get_the_post_thumbnail($photos[$i]->ID);

// get the src for that image
$pattern = '/src="([^"]*)"/';
preg_match($pattern, $image, $matches);
$src = $matches[1];
unset($matches);

In the pattern to grab the title or the alt, you could simply use $pattern = '/title="([^"]*)"/'; to grab the title or $pattern = '/title="([^"]*)"/'; to grab the alt. Sadly, my regex isn't good enough to grab all three (alt/title/src) with one pass though.

Here's A PHP Function I hobbled together from all of the above info for a similar purpose, namely adjusting image tag width and length properties on the fly ... a bit clunky, perhaps, but seems to work dependably:

function ReSizeImagesInHTML($HTMLContent,$MaximumWidth,$MaximumHeight) {

// find image tags
preg_match_all('/<img[^>]+>/i',$HTMLContent, $rawimagearray,PREG_SET_ORDER); 

// put image tags in a simpler array
$imagearray = array();
for ($i = 0; $i < count($rawimagearray); $i++) {
    array_push($imagearray, $rawimagearray[$i][0]);
}

// put image attributes in another array
$imageinfo = array();
foreach($imagearray as $img_tag) {

    preg_match_all('/(src|width|height)=("[^"]*")/i',$img_tag, $imageinfo[$img_tag]);
}

// combine everything into one array
$AllImageInfo = array();
foreach($imagearray as $img_tag) {

    $ImageSource = str_replace('"', '', $imageinfo[$img_tag][2][0]);
    $OrignialWidth = str_replace('"', '', $imageinfo[$img_tag][2][1]);
    $OrignialHeight = str_replace('"', '', $imageinfo[$img_tag][2][2]);

    $NewWidth = $OrignialWidth; 
    $NewHeight = $OrignialHeight;
    $AdjustDimensions = "F";

    if($OrignialWidth > $MaximumWidth) { 
        $diff = $OrignialWidth-$MaximumHeight; 
        $percnt_reduced = (($diff/$OrignialWidth)*100); 
        $NewHeight = floor($OrignialHeight-(($percnt_reduced*$OrignialHeight)/100)); 
        $NewWidth = floor($OrignialWidth-$diff); 
        $AdjustDimensions = "T";
    }

    if($OrignialHeight > $MaximumHeight) { 
        $diff = $OrignialHeight-$MaximumWidth; 
        $percnt_reduced = (($diff/$OrignialHeight)*100); 
        $NewWidth = floor($OrignialWidth-(($percnt_reduced*$OrignialWidth)/100)); 
        $NewHeight= floor($OrignialHeight-$diff); 
        $AdjustDimensions = "T";
    } 

    $thisImageInfo = array('OriginalImageTag' => $img_tag , 'ImageSource' => $ImageSource , 'OrignialWidth' => $OrignialWidth , 'OrignialHeight' => $OrignialHeight , 'NewWidth' => $NewWidth , 'NewHeight' => $NewHeight, 'AdjustDimensions' => $AdjustDimensions);
    array_push($AllImageInfo, $thisImageInfo);
}

// build array of before and after tags
$ImageBeforeAndAfter = array();
for ($i = 0; $i < count($AllImageInfo); $i++) {

    if($AllImageInfo[$i]['AdjustDimensions'] == "T") {
        $NewImageTag = str_ireplace('width="' . $AllImageInfo[$i]['OrignialWidth'] . '"', 'width="' . $AllImageInfo[$i]['NewWidth'] . '"', $AllImageInfo[$i]['OriginalImageTag']);
        $NewImageTag = str_ireplace('height="' . $AllImageInfo[$i]['OrignialHeight'] . '"', 'height="' . $AllImageInfo[$i]['NewHeight'] . '"', $NewImageTag);

        $thisImageBeforeAndAfter = array('OriginalImageTag' => $AllImageInfo[$i]['OriginalImageTag'] , 'NewImageTag' => $NewImageTag);
        array_push($ImageBeforeAndAfter, $thisImageBeforeAndAfter);
    }
}

// execute search and replace
for ($i = 0; $i < count($ImageBeforeAndAfter); $i++) {
    $HTMLContent = str_ireplace($ImageBeforeAndAfter[$i]['OriginalImageTag'],$ImageBeforeAndAfter[$i]['NewImageTag'], $HTMLContent);
}

return $HTMLContent;

}

Here is THE solution, in PHP:

Just download QueryPath, and then do as follows:

$doc= qp($myHtmlDoc);

foreach($doc->xpath('//img') as $img) {

   $src= $img->attr('src');
   $title= $img->attr('title');
   $alt= $img->attr('alt');

}

That's it, you're done !

I have read the many comments on this page that complain that using a dom parser is unnecessary overhead. Well, it may be more expensive than a mere regex call, but the OP has stated that there is no control over the order of the attributes in the img tags. This fact leads to unnecessary regex pattern convolution. Beyond that, using a dom parser provides the additional benefits of readability, maintainability, and dom-awareness (regex is not dom-aware).

I love regex and I answer lots of regex questions, but when dealing with valid HTML there is seldom a good reason to regex over a parser.

In the demonstration below, see how easy and clean DOMDocument handles img tag attributes in any order with a mixture of quoting (and no quoting at all). Also notice that tags without a targeted attribute are not disruptive at all -- an empty string is provided as a value.

Code: (Demo)

$test = <<<HTML
<img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny" />
<img src='/image/pricklycactus.jpg' title='Roger the cactus' alt='a big green prickly cactus' />
<p>This is irrelevant text.</p>
<img alt="an annoying white cockatoo" title="Polly the cockatoo" src="/image/noisycockatoo.jpg">
<img title=something src=somethingelse>
HTML;

libxml_use_internal_errors(true);  // silences/forgives complaints from the parser (remove to see what is generated)
$dom = new DOMDocument();
$dom->loadHTML($test);
foreach ($dom->getElementsByTagName('img') as $i => $img) {
    echo "IMG#{$i}:\n";
    echo "\tsrc = " , $img->getAttribute('src') , "\n";
    echo "\ttitle = " , $img->getAttribute('title') , "\n";
    echo "\talt = " , $img->getAttribute('alt') , "\n";
    echo "---\n";
}

Output:

IMG#0:
    src = /image/fluffybunny.jpg
    title = Harvey the bunny
    alt = a cute little fluffy bunny
---
IMG#1:
    src = /image/pricklycactus.jpg
    title = Roger the cactus
    alt = a big green prickly cactus
---
IMG#2:
    src = /image/noisycockatoo.jpg
    title = Polly the cockatoo
    alt = an annoying white cockatoo
---
IMG#3:
    src = somethingelse
    title = something
    alt = 
---

Using this technique in professional code will leave you with a clean script, fewer hiccups to contend with, and fewer colleagues that wish you worked somewhere else.

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