regex101: Find html tag opening for tag with specific class.

^start of line

Non-Capturing Group(?:(?<!\/\/|\/\*|<!--).)*

*repeats the group contents below any number of times:

Negative Lookbehind(?<!\/\/|\/\*|<!--)

1st Alternative\/\/

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

2nd Alternative\/\*

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\*the literal * (42₁₀ / 52₈ / 2A₁₆)

3rd Alternative<!--

<!--the literal text <!--

.any character (except for line terminators)

Comment:check if commented out

<the literal text <

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case insensitive)

Character Class[a-z0-9]*?

*?matches any number of characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case insensitive)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

\ban ASCII word boundary

Comment:find start of a tag

Non-Capturing Group(?:.(?![^?]>))+

+repeats the group contents below at least once:

.any character (except for line terminators)

Negative Lookahead(?![^?]>)

Negated Character Class[^?]

?the literal ? (63₁₀ / 77₈ / 3F₁₆)

>the literal > (62₁₀ / 76₈ / 3E₁₆)

Comment:Must not find > between start and class unless ?>

class=the literal text class= (case insensitive)

Group 1(["'])

Character Class["']

"the literal " (34₁₀ / 42₈ / 22₁₆)

'the literal ' (39₁₀ / 47₈ / 27₁₆)

Comment:Find class and opening quotes

Non-Capturing Group(?:(?!\1).)*

*repeats the group contents below any number of times:

Negative Lookahead(?!\1)

\1the text saved by group 1

.any character (except for line terminators)

\ban ASCII word boundary

matchthe literal text match (case insensitive)

\ban ASCII word boundary

Non-Capturing Group(?:(?!\1).)*

*repeats the group contents below any number of times:

Negative Lookahead(?!\1)

\1the text saved by group 1

.any character (except for line terminators)

Comment:see if our tag is in between the quotes

\1the text saved by group 1

Comment:closing quotes

.*any character (except for line terminators), repeated any number of times

Negative Lookbehind(?<!\?)

\?the literal ? (63₁₀ / 77₈ / 3F₁₆)

> the literal text >

Comment:find first > without ? in front of it

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

U modifier: Ungreedy. Quantifiers are lazy by default. A trailing ? makes a quantifier greedy

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

Search reference

Regular Expression

^(?:(?<!\/\/|\/\*|<!--).)*  #check if commented out
<[a-z][a-z0-9]*?\b          #find start of a tag
(?:.(?![^?]>))+             #Must not find > between start and class unless ?>
class=(["'])                #Find class and opening quotes
(?:(?!\1).)* \bmatch\b (?:(?!\1).)* #see if our tag is in between the quotes
\1                          #closing quotes
.*(?<!\?)>                  #find first > without ? in front of it

Test String
New

<h1 class="match">Match list</h1>

<p class="match">Simple class element.</p>

 <p></p> <h6 class='more match classes'> more classes different comma</h6>

 <fdf <?php echo 'data="extra data test to disturb the page."'; ?> class='incluEdit match classes' > dffd

     <div class='hoppa match more classes' <?=$zooi ?>  > nested elements </div></div>

// <h1 class='match more classes'> no Match list</h1>
/* <h1 class='match more classes'> no Match list</h1>
<!-- <h1 class='match more classes'> no Match list</h1>


<p class='nomatch more classes'>shouldn't match</p>

Regular Expression

Test StringNew

Test String
New