$re = '/(\d{1,3}(?:,\d{1,3})*)+(?= USD)/';
$str = '<div class="priceitem"> 1,231,098 USD <span id="XUwt-price-mb-aE068a15dcca8E168a15dcca8-tooltipIcon" class="tooltip-icon afterPrice info-icon"> <svg class="" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 200 200" width="100%" height="100%"><use xlink:href="#common-icon-icon-info"></use></svg> </span> <br></div>';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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