RE: [PHP] Anyone have a tool/script to convert <? to <?php (but not <?=)

I've started writing the tool (which I will post when finished for others to use). However, I have a few questions about preg_replace(): How do I search for '$' literal? I thought it was just backslash escape it but that isn't matching (as indicated by the semi-colon in the output) php > echo preg_replace("/<\?=(\$.+?);?\s*\?/", '<?= '.trim("$1").' ?>', 'Username: <?= $username; ?>')."\n"; Username: <?= $username; ?> For fun I tried without the \$ and just $ but same thing. php > echo preg_replace("/<\?=($.+?);?\s*\?/", '<?= '.trim("$1").' ?>', 'Username: <?= $username; ?>')."\n"; Username: <?= $username; ?> Taking off the $ check all together I get the match, but then how can I apply trim() to the match? The documentation seems to imply this should work no? http://php.net/preg_replace php > echo preg_replace("/<\?=(.+?);?\s*\?/", '<?= '.trim("$1").' ?', 'Username: <?= $username; ?>')."\n"; Username: <?= $username ?> For sanity I tried a few other things and it doesn't appear that the chosen function is processing the match variable $1? php > echo preg_replace("/<\?=(.+?);?\s*\?/", '<?= '.trim('$1').' ?', 'Username: <?= $username; ?>')."\n"; Username: <?= $username ?> php > echo preg_replace("/<\?=(.+?);?\s*\?/", '<?= '.md5('$1').' ?', 'Username: <?= $username; ?>')."\n"; Username: <?= 06d3730efc83058f497d3d44f2f364e3 ?> php > echo preg_replace("/<\?=(.+?);?\s*\?/", '<?= '.md5('$1').' ?', 'Username: <?= $foo; ?>')."\n"; Username: <?= 06d3730efc83058f497d3d44f2f364e3 ?> echo preg_replace("/<\?=(.+?);?\s*\?/", '<?= '.md5("$1").' ?', 'Username: <?= $foo; ?>')."\n"; Username: <?= 06d3730efc83058f497d3d44f2f364e3 ?> Notice how the MD5 didn't change, indicating that it's MD5'ing the literal string '$1' and verified by this php > echo md5('$1')."\n"; 06d3730efc83058f497d3d44f2f364e3 *sigh* Ultimately I was able to craft a regex that I think will work in this instance php > echo preg_replace("/<\?=\s*(.+?);?\s*\?/", "<?= $1 ?", 'Username: <?= $username; ?>')."\n"; Username: <?= $username ?> But I'd like to know the answers to the two questions above for future reference