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PHP script to automatically clean dirty HTML. Removes unnecessary attributes (e.g. style, id, dir), replaces deprecated tags with valid ones (e.g. <b> to <strong>), and strips undesirable tags (e.g <font>). We have used this script to safely clean hundreds of blog posts that were littered with inline styling.
<?php
// List of tags to be replaced and their replacement
$replace_tags = [
'i' => 'em',
'b' => 'strong'
];
// List of tags to be stripped. Text and children tags will be preserved.
$remove_tags = [
'acronym',
'applet',
'b',
'basefont',
'big',
'bgsound',
'blink',
'center',
'del',
'dir',
'font',
'frame',
'frameset',
'hgroup',
'i',
'ins',
'kbd',
'marquee',
'nobr',
'noframes',
'plaintext',
'samp',
'small',
'span',
'strike',
'tt',
'u',
'var'
];
// List of attributes to remove. Applied to all tags.
$remove_attribs = [
'class',
'style',
'lang',
'width',
'height',
'align',
'hspace',
'vspace',
'dir'
];
// Your HTML code
$html = '<p class="large-font", style="color: red"><b>Hello</b> <span style="margin-left: 1em">world!</span><br>How are you doing?</p>';
function replaceTags($html, $tags) {
// Clean the HTML
$html = '<div>' . $html . '</div>'; // Workaround to get the HTML back from DOMDocument without the <html><head> and <body> tags
$dom = new DOMDocument;
$dom->loadHTML($html);
$html = substr($dom->saveHTML($dom->getElementsByTagName('div')->item(0)), 5, -6);
// Use simple string replace to replace tags
foreach($tags as $search => $replace) {
$html = str_replace('<' . $search . '>', '<' . $replace . '>', $html);
$html = str_replace('<' . $search . ' ', '<' . $replace . ' ', $html);
$html = str_replace('</' . $search . '>', '</' . $replace . '>', $html);
}
return $html;
}
function stripTags($html, $tags) {
// Remove all attributes from tags to be removed
$html = '<div>' . $html . '</div>';
$dom = new DOMDocument;
$dom->loadHTML($html);
foreach($tags as $tag){
$nodes = $dom->getElementsByTagName($tag);
foreach($nodes as $node) {
// Remove attributes
while($node->attributes->length) {
$node->removeAttribute($node->attributes->item(0)->name);
}
}
}
$html = substr($dom->saveHTML($dom->getElementsByTagName('div')->item(0)), 5, -6);
// Strip tags using string replace
foreach($tags as $tag){
$html = str_replace('<' . $tag . '>', '', $html);
$html = str_replace('</' . $tag . '>', '', $html);
}
return $html;
}
function stripAttributes($html, $attribs) {
// Find all nodes that contain the attribute and remove it
$html = '<div>' . $html . '</div>';
$dom = new DOMDocument;
$dom->loadHTML($html);
$xPath = new DOMXPath($dom);
foreach($attribs as $attrib) {
$nodes = $xPath->query('//*[@' . $attrib . ']');
foreach($nodes as $node) $node->removeAttribute($attrib);
}
return substr($dom->saveHTML($dom->getElementsByTagName('div')->item(0)), 5, -6);
}
$html = replaceTags($html, $replace_tags);
$html = stripTags($html, $remove_tags);
$html = stripAttributes($html, $remove_attribs);
echo $html;
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