$re = '/-a----\s{2,}[0-9]\/[0-9]{1,}\/201[0-9]\s{1,}[0-9]{1,}:[0-9]{2} [AP]M\s{2,}[0-9]{2,}\s/m';
$str = '-a---- 7/30/2017 4:28 PM 201 textfile1.txt
-a---- 6/9/2016 4:03 PM 44 textfile2.txt
-a---- 6/22/2017 12:10 PM 137 textfile3.txt
-a---- 6/6/2017 7:24 PM 8269721 otherfile.com
-a---- 3/11/2016 4:22 PM 3370 otherfile.bat';
$subst = " Call Deletefile(MyMaster.ZSVCPATH'\\firmware\\";
$result = preg_replace($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