$re = '~\b[a-zA-Z]{1,2}\d{3,5}[a-zA-Z]?\b~m';
$str = 'M394
,MP4245)
TD493!
X4958A
V49534@
U394U
A5909.
TED492
R32
R4!3
U394UU
A5909AA
5349A';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php