Conditional search and replace using PHP and regex

Question

I need to hide all "p" tags in a HTML file that have an inline style with a "left" offset of 400 or more.

I'm hoping some clever regex will replace "left:XXX" with "display:none" should "xxx" be 400 or more.

For example, this:

<p style="position:absolute;top:98px;left:472px;white-space:nowrap">

...would need to be replaced with this:

<p style="position:absolute;top:98px;display:none;white-space:nowrap">

It seems simple enough logic, but the regex and PHP is mind boggling for me.

Here is what I've been trying to do, but I can only get it to work line-by-line:

$width = preg_match("left:(.*?)px",$contents);
if ($width >399)
{
    $contents = preg_replace('/left:(.*?)px/', "display:none", $contents);
}

Any suggestions greatly appreciated! :)

Wonko

What do you want exactly ?! Do you want to replace line2 instead line1 ? — user4795756
– user4795756, Commented May 15, 2015 at 22:23
Good question Fatemeh, thanks for asking. I need to replace "left:xxx" with "display:none" if "xxx" is greater than 400. — Wonko the Sane
– Wonko the Sane, Commented May 15, 2015 at 22:26
@WonkotheSane Sorry, but Stack Overflow is not a code writing service. You need to first write code that shows a significant attempt to solve the problem and show any research you did. You also need to explain in detail what the problem with the current code is so that it can be clearer to those answering. You can read all about it on the how to ask guide page. If you want code to simply be written for you, I suggest you instead hire a freelance programmer. — Anonymous
– Anonymous, Commented May 15, 2015 at 22:31
Now, you say greater than 400, and before it was offset of 400 or more. What is the exact requirement? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented May 15, 2015 at 22:33
@WonkotheSane: You can use this regex: $re = "/<p\\s+[^<]*style=\"[^\"]*left:\\K(?:[4-9][0-9][0-9]|[1-9][0-9][0-9][0-9])px/i"; (to be replaced with display:none). I am not posting, since most probably this question is going to be closed by "xeger"-people. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented May 15, 2015 at 22:39

Casimir et Hippolyte · Accepted Answer · 2015-05-15 23:55:53Z

2

Don't believe that regex will solve all the problem of the world:

Use DOMDocument to extract the p tags with a style attribute, extract the "left" value with a regex pattern from the style attribute and then proceed to the replacement when the "left" value is greater or equal to 400 (test this with a simple comparison).

$dom = new DOMDocument;
$dom->loadHTML($html);

$pTags = $dom->getElementsByTagName('p');

foreach($pTags as $pTag) {
    if ($pTag->hasAttribute('style')) {
        $style = $pTag->getAttribute('style');
        $style = preg_replace_callback(
            '~(?<=[\s;]|^)left\s*:\s*(\d+)\s*px\s*(?:;|$)~i',
            function ($m) {
                return ($m[1] > 399) ? 'display:none;' : $m[0];
            },
            $style
        );
        $pTag->setAttribute('style', $style);
    }
}

$result = $dom->saveHTML();

EDIT: in the worst scenario, the style attribute may contain display:block; or display with a value other than none after the left value. To avoid any problem, it is better to put display:none at the end.

$style = preg_replace_callback(
    '~(?<=[\s;]|^)left\s*:\s*(\d+)\s*px\s*(;.*|$)~i',
    function ($m) {
        return ($m[1] > 399) ? $m[2]. 'display:none;' : $m[0];
    },
    $style
);

edited May 15, 2015 at 23:55

answered May 15, 2015 at 22:53

Casimir et Hippolyte

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13 Comments

Wonko the Sane Over a year ago

Woah, it works perfectly. I would never have thought of DOMDocument. Thanks for putting me on the right track, you rock!

user4795756 Over a year ago

I can't understand what is $m ?

Casimir et Hippolyte Over a year ago

@Fatemeh: $m is the match array, index 0 is the whole match and other indexes are capture groups (1 for the first, 2 for the second, etc.)

user4795756 Over a year ago

aha, but $m[1] means one error was found in the matching ?

Casimir et Hippolyte Over a year ago

@Fatemeh: No, $m[1] is the content captured between these parenthesis in the pattern: (\d+) (so it is the value of the "left" parameter, the number).

|

user4795756 · Accepted Answer · 2015-05-15 23:03:45Z

I've tested it and it works correctly:

$string = '<p style="position:absolute;top:98px;left:472px;white-space:nowrap">';

 $test = str_replace('left:', 'display:none;[', $string );
 $test = str_replace('white-space', ']white-space', $test );
 $out = delete_all_between('[', ']', $test);
 print($out); // output

function delete_all_between($beginning, $end, $string) {
  $beginningPos = strpos($string, $beginning);
  $endPos = strpos($string, $end);
  if ($beginningPos === false || $endPos === false) {
    return $string;
  }

  $textToDelete = substr($string, $beginningPos, ($endPos + strlen($end)) - $beginningPos);

  return str_replace($textToDelete, '', $string);
}

output:

<p style="position:absolute;top:98px;display:none;white-space:nowrap">

enjoy it ... !

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