Question

I’m Having trouble with regex. Never fully understood it the real question is: does anybody have a good site that explains the difference between the expression instead of just posting stuff like

$regexp = "/^[^0-9][A-z0-9_]+([.][A-z0-9_]+)*[@][A-z0-9_]+([.][A-z0-9_]+)*[.][A-z]{2,4}$/";

then prattling off what that line as a whole will do. Rather then what each expression will do. I’ve tried googling many different versions of preg_replace and regex tutorial but they all seem to assume that we already know what stuff like \b[^>]* will do.

Secondary. The reason i am trying to do this:
i want to turn

<span style="color: #000000">*ANY NUMBER*</span>

into

<span style="color: #0000ff">*ANY NUMBER*</span>

a few variations that i have already tried some just didnt work some make the script crap out.

$data = preg_replace("/<span style=\"color: #000000\">([0-9])</span>/", "<span style=\"color: #FFCC00\">$1</span>", $data);//just tried to match atleast 0-9

$data = preg_replace("/<span style=\"color: #000000\"\b[^>]*>(.*?)</span>/", "<span style=\"color: #FFCC00\">$1</span>", $data);

$data = preg_replace("/<span style=\"color: #000000\"\b[^>]*>([0-9])</span>/", "<span style=\"color: #FFCC00\">$1</span>", $data);

The answer to this specific problem is not nearly as important to me as a site so check goes to that. Tried alot of different sites and i am pretty sure its not above my comprehension i just cannot find a good for all the bad tutorial/example farm. Normal fallbacks of w3 and phpdotnet dont have what i need this time.

EDIT1 For those of you who end up in here looking for a similar answer:

$data = preg_replace("/<span style=\"color: #000000\">([0-9]{1,})<\/span>/", "<span style=\"color: #FFCC00\">$1</span>", $data);

Did what it needed to. Sadly it was one of the first things i tried but because i didnt put </span> instead of it was not working and i do not know if “[0-9]{1,}” is the MOST appropriate way of matching any number (telling it to match any integer 0-9 with [0-9] atleast once and as many times as it can with {1,} it still fit the purpose)

ROY Finley Posted:
http://www.macronimous.com/resources/writing_regular_expression_with_php.asp
Its a good site with a list of expression definitions and a good example workup below.

Also:
regular-expressions.info/tutorial.html was posted a few times. Its a slower more indepth walk through but if you are stuck like i am its good.

Will pop in about regex101 and the parsers after i have a chance to play with them.

EDIT2
DWright posted a book link below “Mastering Regular Expressions”. If you look at regex and cannot make heads or tails of the convolution of characters it is DEFINITELY worth picking it up. Took about an hour and a half to read about half but that is no time compared to the hours spend on google and the mess up work arounds used to avoid it.

Also the html parse linked below would be right for this particular problem.

Answer 1

To have a regex explained, you can have a look at Regex101. To actually learn regular expressions (which I recommend), this is a pretty good, in-depth tutorial. After you have read that, the PCRE documentation on PHP.net shouldn’t seem to arcane any more, and reading it will help you get your head around some specific differences for PHP.

However, for the problem at hand, you shouldn’t actually be using regex at all. A DOM parser is the way to go. Here is a very convenient to use 3rd party one, and this is what PHP brings along itself. As mentioned by hakre,here is a more extensive list of libraries available for this purpose.

Another general recommendation for regexes in PHP: use single quotes '/pattern/', because double quotes cause a lot of trouble with escape sequences (you need to double some backslashes otherwise).

Finally, the reason you get errors is that your regex delimiter (you use /) shows up in your pattern (in the closing span tag) without it being escaped. That means the engine thinks that the pattern ends at the first / and that span>/ are 6 different modifiers (most of which don’t actually exist). You could either escape the delimiter like <\/span> or even better, change the delimiter (you can use pretty much anything) like '~yourPattern/Here~'.

Edit: Since I posted this answer, two new websites have been released which try to explain regular expressions by visualising them. Right now they only support the (quite limited) JavaScript flavor, but it’s a good point to start:

• Regexper
• Debuggex