replace tag by TAG with preg
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<?php
$file=file_get_contents('yandex.html');
if($file)
{
$new_file = preg_replace_callback('<[0-9a-z]>',function ($matches) { strtoupper($matches[0]);},$file);
file_put_contents('yandex.html',$new_file);
};
echo($file);
Php
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