使用php preg_match从论坛报价中获取ID

Question

I've been using preg_match to try and get an id from a quote in my forums I have written. This is what I have so far.

$quote = '[quote]19[\quote] This is a reply to the quote.';

$get = '/([quote])([0-9])([\quote])/';

$id = '';

preg_match($get, $quote, $id);

echo $id[0];

Unfortunately this doesn't give me the result I was hoping for and I have tried many variations and even tried preg_replace in hopes that might give me what I need but After a lot of reading on stack overflow I think preg_match is the way to go. I just can't seem to get what I want which is the id in between the quote tags.

My experience with preg is limited at best and I've tried my best to try to get it to work but unfortunately it is beyond my current knowledge so any assistance would be appreciated.

Answer 1

Hints

• [ and ] are used as character class delimiters.
  They must be escaped \\[, \\] when to be taken literally.
  The definition [0-9] means exactly this: the character class of digits.
• (…) brackets embrace the result group.
  If you wish to extract the numeric data between [quote] and [\\quote] only ([0-9]*?) should be in brackets. The result would then be in $id[1] (group # 1).
• The backslash "\\" character in [\\quote] must be escaped too, as it is the escape character itself: [\\\\\\\\quote] (4 times \\, since it is interpreted twice; somehow tricky, I know).
  Btw: maybe [/quote] is meant; that would make it easier (?)

Code

<?php
    $quote1 = '[quote]19[\quote] This is a reply to the quote.';
    $quote2 = '[quote]19[/quote] This is a reply to the quote.';
    // $get = '/\[quote\]([0-9].*?)\[\quote\]/';
    $get1 = '%\[quote\]([0-9]*?)\[\\\\quote\]%';
    $get2 = '%\[quote\]([0-9]*?)\[/quote\]%';
    $id = '';
    preg_match($get1, $quote1, $id);
    echo '$get1,$quote1 :: ' . $id[1] . '<br />';
    preg_match($get2, $quote2, $id);
    echo '$get2,$quote2 :: ' . $id[1] . '<br />';
?>

Output:
$get1,$quote1 :: 19
$get2,$quote2 :: 19

Regex commented

    \[          # Match the character “[” literally
    quote       # Match the characters “quote” literally
    \]          # Match the character “]” literally
    (           # Match the regular expression below and capture its match into backreference number 1
       [0-9]       # Match a single character in the range between “0” and “9”
          *?          # Between zero and unlimited times, as few times as possible, expanding as needed (lazy)
    )
    \[          # Match the character “[” literally
        \\\\       # Match the character “\” literally
    quote       # Match the characters “quote” literally
    \]          # Match the character “]” literally