$re = '/<.+?>/';
$str = '<!-- wp:paragraph {"style":{"color":{"text":"#ffffff","background":"#709372"}}} -->
<p class="has-text-color has-background" style="background-color:#709372;color:#ffffff">This is a paragraph block with a <strong>background</strong>. Professionally productize highly efficient results with world-class core competencies. 5 < 1 Objectively matrix leveraged architectures vis-a-vis error-free applications. Completely maximize customized portals via fully <researched metrics. Enthusiastically generate premier action items through web-enabled e-markets. Efficiently parallel task holistic intellectual capital and client-centric markets.<br></p>
<!-- /wp:paragraph -->
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php