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<!DOCTYPE html>
<html>
<body>
<h1>Regex Modifier: \u</h1>
<p>How many occurences of the digit "9" are in the text "W3Schools has been live since 1999"?:</p>
<p>Use the hexadecimal equivalence of 9 which is 0039.</p>
<?php
$txt = "W3Schools has been live since 1999";
$pattern = "/\u{0039}/";
echo preg_match_all($pattern, $txt);
?>  
<p>The matches were found here:</p>
<?php
echo preg_replace($pattern, "#", $txt);
?>  
<p>(Each match was replaced by a # character)</p>
</body>
</html>

Regex Modifier: \u

How many occurences of the digit "9" are in the text "W3Schools has been live since 1999"?:

Use the hexadecimal equivalence of 9 which is 0039.

3

The matches were found here:

W3Schools has been live since 1###

(Each match was replaced by a # character)