PHP正则表达式帮助

Question

I'm working on fixing a few bugs / adding features to a site somebody else built. Can anyone tell me what the following regexes do? I'm semi familiar with regular expressions, but I haven't the foggiest idea what these are trying to accomplish.

$qsReplace = preg_replace('/\\\t/', "\t", $qsReplace);
$qsReplace = preg_replace('/\\\/', '\\\\\\', $qsReplace);
$qsReplace = preg_replace('/\$([0-9])/','\$````~~~~$1', $qsReplace);
$queryString = preg_replace('/\$\`\`\`\`\~\~\~\~([0-9])/','\$$1', $queryString);

I suspect that whoever coded this was a little bit strange, but I'm not sure.

Answer 1

The third one finds a dollar sign followed by a digit and inserts four backticks and four tildes between the number and the dollar sign. The fourth one removes these backticks and tildes between a dollar and the number.

I would suspect some more data juggling going on between the two and a hope that no input ever would contain four backticks followed by four tildes...

Answer 2

1. Replace an escaped \\t with a tab (\\t)
2. Escapes double backslashes
3. Finds a dollar sign followed by a digit and inserts four backticks and four tildes between the number and the dollar sign.
4. Removes these backticks and tildes between a dollar and the number.

(3 & 4 thanks to chx)

Answer 3

Converts \\t into and actual tab

• $qsReplace = preg_replace('/\\\\\\t/', "\\t", $qsReplace);

Escapes Double backslashes, Can be replaced with addslhases();

• $qsReplace = preg_replace('/\\\\\\/', '\\\\\\\\\\\\', $qsReplace);

Finds a $ followed by a digit such as $01 and replaces with backtick x4 + ~ x4 (pre)

• $qsReplace = preg_replace('/\\$([0-9])/','\\$````~~~~$1', $qsReplace);

Removes the $ , backtick , ~

• $queryString = preg_replace('/\\$\\`\\`\\`\\`\\~\\~\\~\\~([0-9])/','\\$$1', $queryString);

Obviously the last programmer did not understand a few things.