Code for https://b-alidra.com/strip-quoted-text-from-html-emails/

common_tags.php

<?php
$els_to_remove = [
  'blockquote', // Standard quote block tag
  'div.moz-cite-prefix', // Thunderbird
  'div.gmail_extra', 'div.gmail_quote', // Gmail
  'div.yahoo_quoted' // Yahoo
];
?>

remove_common_tags.php

<?php
$dom = new PHPHtmlParser\Dom;
$dom->load($message_body);

foreach ($els_to_remove as $el) {
    $founds = $dom->find($el)->toArray();
    foreach ($founds as $f) {
        $f->delete();
        unset($f);
    }
}
?>

remove_empty_tags.php

<?php
// Let's remove empty tags
$els = $dom->find('p,span,b,strong,div')->toArray();
foreach ($els as $e) {
    $html = trim($e->innerHtml());
    if (empty($html) || $html == "&nbsp;") {
        $e->delete();
        unset($e);
    }
}
?>

remove_outlook.php

<?php
// Example of Outlook quote:
// <div>
//    <hr id="stopSpelling">
//    Date: Fri. 20 May 2016 17:40:24 +0200
//    Subject: Votre facture Selon devis DEV201605201
//    From: xxxxxx@microfactures.com
//    To: xxxxxx@hotmail.fr
//    Lorem ipsum dolor sit amet consectetur...
// </div>

// The idea is to delete #stopSpelling's parent...

$hr = $dom->find('#stopSpelling', /*nth result*/0);
if (null !== $hr) {
    $hr->getParent()->delete();
}
?>

remove_roundcube.php

<?php
// Roundcube adds a paragraph with a sentence like this one, just
// before the quote:
// "Le 21-05-2016 02:25, AB Prog - Belkacem Alidra a écrit :"
// Let's remove it
$pattern = '/Le [0-9]{2}-[0-9]{2}-[0-9]{4} [0-9]{2}:[0-9]{2}, [^:]+ a &amp;eacute;crit&amp;nbsp;:/';
$ps = $dom->find('p')->toArray();
foreach ($ps as $p) {
    if (preg_match($pattern, $p->text())) {
        $p->delete();
        unset($p);
    }
}
?>

return_cleaned_message.php

<?php return $dom->root->innerHtml(); ?>

strip_quoted_text_from_emails.php

<?php
/**
 * Remove the quoted parts from the message body.
 *
 * It actually handles:
 * - Standard <blockquote>...</blockquote>
 * - Google
 * - Yahoo
 * - Thunderbird
 * - OSX Mail Client
 * - Roundcube
 *
 * @param String $message_body
 *        The incoming or outcoming message to be cleaned
 *
 * @return String
 *         The cleaned message
 */
public static function strip_quotes_from_message($message_body)
{
    $els_to_remove = [
        'blockquote',                           // Standard quote block tag
        'div.moz-cite-prefix',                  // Thunderbird
        'div.gmail_extra', 'div.gmail_quote',   // Gmail
        'div.yahoo_quoted'                      // Yahoo
    ];

    $dom = new PHPHtmlParser\Dom;
    $dom->load($message_body);

    foreach ($els_to_remove as $el) {
        $founds = $dom->find($el)->toArray();
        foreach ($founds as $f) {
            $f->delete();
            unset($f);
        }
    }

    // Outlook doesn't respect
    // http://www.w3.org/TR/1998/NOTE-HTMLThreading-0105#Appendix%20B
    // We need to detect quoted replies "by hand"
    //
    // Example of Outlook quote:
    //
    // <div>
    //      <hr id="stopSpelling">
    //      Date: Fri. 20 May 2016 17:40:24 +0200<br>
    //      Subject: Votre facture Selon devis DEV201605201<br>
    //      From: xxxxxx@microfactures.com<br>
    //      To: xxxxxx@hotmail.fr<br>
    //      Lorem ipsum dolor sit amet consectetur adipiscing...
    // </div>
    //
    // The idea is to delete #stopSpelling's parent...

    $hr  = $dom->find('#stopSpelling', /*nth result*/0);
    if (null !== $hr) {
        $hr->getParent()->delete();
    }

    // Roundcube adds a <p> with a sentence like this one, just
    // before the quote:
    // "Le 21-05-2016 02:25, AB Prog - Belkacem Alidra a écrit :"
    // Let's remove it
    $pattern = '/Le [0-9]{2}-[0-9]{2}-[0-9]{4} [0-9]{2}:[0-9]{2}, [^:]+ a &eacute;crit&nbsp;:/';
    $ps = $dom->find('p')->toArray();
    foreach ($ps as $p) {
        if (preg_match($pattern, $p->text())) {
            $p->delete();
            unset($p);
        }
    }

    // Let's remove empty tags like <p> </p>...
    $els = $dom->find('p,span,b,strong,div')->toArray();
    foreach ($els as $e) {
        $html = trim($e->innerHtml());
        if (empty($html) || $html == "&nbsp;") {
            $e->delete();
            unset($e);
        }
    }

    return $dom->root->innerHtml();
}
?>

strip_quotes_from_message.php

<?php function strip_quotes_from_message($message_body) ?>