PHP正则表达式删除前导和尾随 <br /> 内 <p> 标签

Question

I can't figure this out for the life of me.

I need a regex expression that will strip out any leading or trailing <br> tags within <p> tags.

For example.

<p> <br />Some test text. <br /> Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. <br /><br /><br /> </p>

Should become...

<p>Some test text. <br /> Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text.</p>

I feel as though this should be very simple but I've hit a road-block. Any help would be greatly appreciated.

Answer 1

You just need a look-ahead and look-behind for <p> and </p> , and a non-capturing group for 1 or more occurrences of some variation of <br> .

For matching leading <br/> tags:

(?<=<p>)(?:\s*<br\s*\/?>)+\s*

For matching trailing <br/> tags:

(?:\s*<br\s*\/?>)+\s*(?=<\/p>)

Both together:

(?<=<p>)(?:\s*<br\s*\/?>)+\s*|(?:\s*<br\s*\/?>)+\s*(?=<\/p>)

Regex101 Demo

Answer 2

We can do this without regular expressions.

// Method1 :: Finding and replacing unwanted tags
$str1 = '<p> <br />Some test text. <br /> Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. <br /><br /><br /></p>';

$findTags = array('<br>', '<br />');
$replacement = array();

// Case insensitive replacement
$str1 = str_ireplace($findTags, $replacement, $str1);
print_r($str1);

// Method 2:: Stripping all HTML tags except allowed tags

$str2 = '<p> <br />Some test text. <br /> Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. Some test text. <br /><br /><br /></p>';
$str2 = strip_tags($str2, '<p>');

echo $str2;
?>

Reference Links:

http://php.net/manual/en/function.str-replace.php

http://php.net/manual/en/function.str-ireplace.php

http://php.net/manual/en/function.strip-tags.php