Warning Undefined variable userid in C Apache24 htdocs MIS user pages user change password php on line 158

Question

I'm running a PHP script and continue to receive errors like:

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Warning: Undefined variable $userid in C:\Apache24\htdocs\MIS\user\pages\user_change_password.php on line 158

My Line No 158  (HTML & PHP) look a like:-

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<div class="form-group"><label for="userid" style='font-weight:bold;color:#996666;'>User ID:-&nbsp;</label><?Php echo '<font color="#315E8C"><strong>'. $userid.'</strong></font>'?>

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What is the meaning of these error messages?

How to fix this?