Apply PHP regex replace on a multi-line repeated pattern - php

Question

Let's say I have this input:
I can haz a listz0rs!
# 42
# 126
I can haz another list plox?
# Hello, world!
# Welcome!
I want to split it so that each set of hash-started lines becomes a list:
I can haz a listz0rs!
<ul>
<li>42</li>
<li>126</li>
</ul>
I can haz another list plox?
<ul>
<li>Hello, world!</li>
<li>Welcome!</li>
</ul>
If I run the input against the regex "/(?:(?:(?<=^# )(.*)$)+)/m", I get the following result:
Array
(
[0] => Array
(
[0] => 42
)
[1] => Array
(
[0] => 126
)
[2] => Array
(
[0] => Hello, world!
)
[3] => Array
(
[0] => Welcome!
)
)
This is fine and dandy, but it doesn't distinguish between the two different lists. I need a way to either make the quantifier return a concatenated string of all the occurrences, or, ideally, an array of all the occurrences.
Ideally, this should be my output:
Array
(
[0] => Array
(
[0] => 42
[1] => 126
)
[1] => Array
(
[0] => Hello, world!
[1] => Welcome!
)
)
Is there any way of achieving this, and if not, is there a close alternative?

Answer 1

If you want to do this with regular expressions, you'll need two. Use the regex ^(#.*\r?\n)+ to match each list and add tags around it. Within each list (as matched by the first regex), search-and-replace ^#.* with <li>$0</li> to add tags around each list item. Both regexes require ^ to match at line breaks (/m flag in PHP).
In PHP you can use preg_replace_callback and preg_replace to achieve this in just a few lines of code.
$result = preg_replace_callback('/^(#.*\r?\n)+/m', 'replacelist', $subject);
function replacelist($groups) {
return "<ul>\n" .
preg_replace('/^#.*/m', ' <li>$0</li>', $groups[0])
. "</ul>\n";
}

Answer 2

I'd say don't try to do it all in a single regex - instead, first use a regex to match sets of consecutive lines that all begin with # signs and wrap those lines with a <ul></ul> pair. Then use a second regex (or not even a regex at all - you could just split on line breaks) to match each individual line and convert it to <li></li> format.

Answer 3

If it was me I would:
explode("\n", $input) into an array where 1 key = line
foreach through that array
whenever you get a line that doesn't start with a #, that's when you add your closing/opening ul tags
Add a little more to deal with unexpected input (like two non hash lines in a row) and you're good.

Answer 4

Looks like Syntax Error has already explained what I'm doing. But here goes the link to a working example.

Answer 5

With structured content like this, I would not do this as a regex. How about another approach?
$your_text = <<<END
I can haz a listz0rs!
# 42
# 126
I can haz another list plox?
# Hello, world!
# Welcome!
END;
function printUnorderedList($temp) {
if (count($temp)>0) {
print "<ul>\n\t<li>" .implode("</li>\n\t<li>", $temp) . "</li>\n</ul>\n";
}
}
$lines = explode("\n", $your_text);
$temp = array();
foreach($lines as $line) {
if (substr($line, 0, 1) == '#') {
$temp[] = trim(substr($line,1));
} else {
printUnorderedList($temp);
$temp = array();
echo $line . "\n";
}
}
printUnorderedList($temp);

Answer 6

You could avoid regex altogether, and simply try a simpler approach by having it read the file, line by line (an array of lines), and every time it encounters a non-hash-started line, it starts a new list. Like so:
// You can get this by using file('filename') or
// just doing an explode("\n", $input)
$lines = array(
'I can haz a listz0rs!',
'# 42',
'# 126',
'I can haz another list plox?',
'# Hello, world!',
'# Welcome!'
);
$hashline = false;
$lists = array();
$curlist = array();
foreach ($lines as $line) {
if ($line[0] == '#')
$curlist[] = $line;
elseif ($hashline) {
$lists[] = $curlist;
$curlist = array();
$hashline = false;
}
}
A little clean-up may be in order, but hopefully it helps.
(after reading new answers, this is basically an indepth explanation of Syntax Error's answer.)
EDIT: You may want it to strip off the # at the beginning of each line too.