Conditional search and replace using PHP and regex - php

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

Answer 1

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
);

Answer 2

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 ... !