$re = '/(<\?)(.*?)(?:$|\?>)/is';
$str = '<?php foo(); ?>
<abc>
<? foo(); ?>
<?php
foo();
bar();
?>
foo();
bar();
<? //also short open tag
foo();
bar();
?><?php
foo();
bar();
';
preg_match_all($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