正则表达式匹配不同html标签内的重量（lbs）

Question

I have an HTML file that contains products information including their weights. I am trying to get the weights(any numbers that precede lbs). occasionally there are space between lbs and the weight number. I came up with the regex: preg_match(">[0-9]+(\\.[0-9][0-9]?)(.*?)lbs/i",fgets($file),$matches); but this is returning everything between the first '>' and 'lbs', it is not practical since there are a lot of tags involved. so what I am trying to accomplish is to get only the number between the character '>' that directly precedes the weight and the characters 'lbs' that follows the weight ignoring the space between.

so in the example below, I want to get 0.94,0.12,0.94. Any help is appreciated.

<td width="513" valign="top">0.94 lbs
<td width="513" valign="top">0.12lbs
<td width="513" valign="top">0.94LBS
<td width="513" valign="top">penguin lover

Noticee that the tags ' <td width="513" valign="top"> ' precedes other characters besides the weight.

Any thoughts, help will be appreciated.

Answer 1

Use:

/(?<=>)[0-9]+(?:\.[0-9][0-9]?)(?=\s*lbs)/i

This uses a lookahead and a lookbehind such that the only thing matched is the decimal number.

Explanation:

(?<=>) Lookbehind to check for a > -- (?<=xxx) means look behind for xxx

[0-9]+(?:\\.[0-9][0-9]?) Your unchanged decimal regex using a non-capturing group (?:xxx)

(?=\\s*lbs) Lookahead for 0-many whitespace characters followed by lbs

Note that you can replace each [0-9] with \\d if you want, they are equivalent.

Example code:

$str = '<td width="513" valign="top">0.94 lbs
        <td width="513" valign="top">0.12lbs
        <td width="513" valign="top">0.94LBS
        <td width="513" valign="top">penguin lover';

preg_match_all("/(?<=>)[0-9]+(?:\.[0-9][0-9]?)(?=\s*lbs)/i",$str,$matches);

print_r($matches[0]);

Output:

 Array ( [0] => 0.94 [1] => 0.12 [2] => 0.94 )

Answer 2

preg_match_all('/[0-9]+(?:\.[0-9]+)(?=\s*lbs)/i', $html, $matches);
print_r($matches[0]);

Regular expression:

[0-9]+         any character of: '0' to '9' (1 or more times)
(?:            group, but do not capture (optional)
  \.           '.' 
  [0-9]+       any character of: '0' to '9' (1 or more times)
)              end of grouping
 (?=           look ahead to see if there is:
  \s*          whitespace (\n, \r, \t, \f, and " ") (0 or more times)
  lbs          'lbs'
)              end of look-ahead

See working demo