regex assistance - php

Question

I am trying to match a semi dynamically generated string. So I can see if its the correct format, then extract the information from it that I need. My Problem is I no matter how hard I try to grasp regex can't fathom it for the life of me. Even with the help of so called generators.
What I have is a couple different strings like the following. [#img:1234567890] and [#user:1234567890] and [#file:file_name-with.ext]. Strings like this pass through are intent on passing through a filter so they can be replaced with links, and or more readable names. But again try as I might I can't come up with a regex for any given one of them.
I am looking for the format: [#word:] of which I will strip the [, ], #, and word from the string so I can then turn around an query my DB accordingly for whatever it is and work with it accordingly. Just the regex bit is holding me back.

Answer 1

Not sure what you mean by generators. I always use online matchers to see that my test cases work. #Virendra almost had it except forgot to escape the [] charaters.
/\[#(\w+):(.*)\]/
You need to start and end with a regex delimeter, in this case the '/' character.
Then we escape the '[]' which is use by regex to match ranges of characters hence the '['.
Next we match a literal '#' symbol.
Now we want to save this next match so we can use it later so we surround it with ().
\w matches a word. Basically any characters that aren't spaces, punctuation, or line characters.
Again match a literal :.
Maybe useful to have the second part in a match group as well so (.*) will match any character any number of times, and save it for you.
Then we escape the closing ] as we did earlier.
Since it sounds like you want to use the matches later in a query we can use preg_match to save the matches to an array.
$pattern = '/\[#(\w+):(.*)\]/';
$subject = '[#user:1234567890]';
preg_match($pattern, $subject, $matches);
print_r($matches);
Would output
array(
[0] => '[#user:1234567890]', // Full match
[1] => 'user', // First match
[2] => '1234567890' // Second match
)
An especially helpful tool I've found is txt2re

Answer 2

Here's what I would do.
<pre>
<?php
$subj = 'An image:[#img:1234567890], a user:[#user:1234567890] and a file:[#file:file_name-with.ext]';
preg_match_all('~(?<match>\[#(?<type>[^:]+):(?<value>[^\]]+)\])~',$subj,$matches,PREG_SET_ORDER);
foreach ($matches as &$arr) unset($arr[0],$arr[1],$arr[2],$arr[3]);
print_r($matches);
?>
</pre>
This will output
Array
(
[0] => Array
(
[match] => [#img:1234567890]
[type] => img
[value] => 1234567890
)
[1] => Array
(
[match] => [#user:1234567890]
[type] => user
[value] => 1234567890
)
[2] => Array
(
[match] => [#file:file_name-with.ext]
[type] => file
[value] => file_name-with.ext
)
)
And here's a pseudo version of how I would use the preg_replace_callback() function:
function replace_shortcut($matches) {
global $users;
switch (strtolower($matches['type'])) {
case 'img' : return '<img src="images/img_'.$matches['value'].'jpg" />';
case 'file' : return ''.$matches['value'].'';
// add id of each user in array
case 'user' : $users[] = (int) $matches['value']; return '%s';
default : return $matches['match'];
}
}
$users = array();
$replaceArr = array();
$subj = 'An image:[#img:1234567890], a user:[#user:1234567890] and a file:[#file:file_name-with.ext]';
// escape percentage signs to avoid complications in the vsprintf function call later
$subj = strtr($subj,array('%'=>'%%'));
$subj = preg_replace_callback('~(?<match>\[#(?<type>[^:]+):(?<value>[^\]]+)\])~',replace_shortcut,$subj);
if (!empty($users)) {
// connect to DB and check users
$query = " SELECT `id`,`nick`,`date_deleted` IS NOT NULL AS 'deleted'
FROM `users` WHERE `id` IN ('".implode("','",$users)."')";
// query
// ...
// and catch results
while ($row = $con->fetch_array()) {
// position of this id in users array:
$idx = array_search($row['id'],$users);
$nick = htmlspecialchars($row['nick']);
$replaceArr[$idx] = $row['deleted'] ?
"<span class=\"user_deleted\">{$nick}</span>" :
"{$nick}";
// delete this key so that we can check id's not found later...
unset($users[$idx]);
}
// in here:
foreach ($users as $key => $value) {
$replaceArr[$key] = '<span class="user_unknown">User'.$value.'</span>';
}
// replace each user reference marked with %s in $subj
$subj = vsprintf($subj,$replaceArr);
} else {
// remove extra percentage signs we added for vsprintf function
$subj = preg_replace('~%{2}~','%',$subj);
}
unset($query,$row,$nick,$idx,$key,$value,$users,$replaceArr);
echo $subj;

Answer 3

You can try something like this:
/\[#(\w+):([^]]*)\]/
\[ escapes the [ character (otherwise interpreted as a character set); \w means any "word" character, and [^]]* means any non-] character (to avoid matching past the end of the tag, as .* might). The parens group the various matched parts so that you can use $1 and $2 in preg_replace to generate the replacement text:
echo preg_replace('/\[#(\w+):([^]]*)\]/', '$1 $2', '[#link:abcdef]');
prints link abcdef