$re = '/.{171}/m';
$str = 'HTTP_services.cgi?FILENAME=%2Fdata%2FGPM_L3%2FGPM_3IMERGM.06%2F2020%2F3B-MO.MS.MRG.3IMERG.20200301-S000000-E235959.03.V06B.HDF5&FORMAT=bmM0Lw&BBOX=-9,114.3,-8,115.8&LABEL=3B-MO.MS.MRG.3IMERG.20200301-S000000-E235959.03.V06B.HDF5.SUB.nc4';
$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