$re = '/<\?php(.*?)\?>/s';
$str = '<html>
<head>
<title>Test</title>
</head>
<body>
<div> <a href="test1.html" title="test"></a>
<?php
$result_array="123";
if ($result_array=="123")
{
?>
<a href="test4.html" title="tesdfhdfhdfht2"></a>
<?php
else{
?>
<a href="test5.html" title="tedfhdfhst"></a>
<?php
}
?>
</div>
</body>
</html>
';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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