$re = '/img src="".+?png"/m';
$str = '<img src=""https://support.comp.com/inlineimages/1413838988355.png""><br><p style=""MARGIN: 0.0in 0.0in 0.0pt;""><br><span style=""font-size: 10.0pt;font-family: Arial , sans-serif;""></span></p><p style=""MARGIN: 0.0in 0.0in 0.0pt;""><br></p><p style=""MARGIN: 0.0in 0.0in 0.0pt;"">The setup is shown below:</p><p style=""MARGIN: 0.0in 0.0in 0.0pt;"">%as2-From%-%srcfilebase%.%srcfileext%<br></p><p style=""MARGIN: 0.0in 0.0in 0.0pt;""><img src=""/inlineimages/1413839088730.png"">';
preg_match_all($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