Loop or Query causing Internal Server Error - php

Question

Heres the story,
I am uploading a list of part numbers on text file via gzip, the reading is successful.
The format is:
"DATE"|"TYPE"|"ID"|"FPN"|"PN"|"IOC"|"FIELD"|"OVAL"|"NVAL"
Sample Value :
"2013-09-10 19:19:08"|"DU"|"10161000001354"|""|"ANTX100P001B24003"|""|"Sub-Category 1"|"Metal Antenna"|"PCB Antenna"
Now the scenario is, I loop on each entry to insert it to database and set notifications for users to see an update about that certain part number and get their email to conduct a mailing later in other page.
the loop code is here :
for($x=1;$x<=count($lines)-1;$x++){
$cur_row = trim(str_replace('"','',$lines[$x]));
$cols = preg_split('/\|/',$cur_row);
$query = sprintf('INSERT INTO `notification_details`(`NDATE`, `NTYP`,`NPID`,`NFPN`,`NPN`,`NIOC`, `NFILD`, `NOV`, `NNV`) VALUES(\'%s\',\'%s\',%s,\'%s\',\'%s\',\'%s\',\'%s\',\'%s\',\'%s\')',$cols[0],$cols[1],$cols[2],$cols[3],$cols[4],$cols[5],$cols[6],$cols[7],$cols[8]);
mysql_query($query);
$query = 'SELECT DISTINCT `id` FROM `project_details` WHERE `prod_id` = \''.$cols[2].'\';';
$result = mysql_query($query);
$count = mysql_num_rows($result);
if($count>0){
$query = 'SELECT MAX(`NID`) FROM `notification_details`';
$result = mysql_query($query);
$row=mysql_fetch_array($result);
$NID = $row[0];
$query = sprintf('INSERT INTO `read_details`(`NID`, `PID`,`ISREAD`) VALUES(%s,%s,1);',$NID,$row['id']);
mysql_query($query);
}
echo $cols[2].".... Done!<br />";
flush();ob_flush();
}
//EMAIL LISTING BLOCK
echo "Listing E-mails...<br />";
$query = 'SELECT B.`proj_user`, C.`email` '
.'FROM `read_details` A, `project_details` B, `login_details` C'
.'WHERE A.`ISREAD` = 1 '
.'AND A.`PID` = B.`id` AND B.`proj_user` = C.`username` '
.'GROUP BY B.`proj_user`';
$result = mysql_query($query);
while($row=mysql_fetch_array($result)){
mysql_query('INSERT INTO `email_details`(`email`,`user`) VALUES(\''.$row[1].'\',\''.$row[0].'\')');
echo $row[1].".... Added!<br />";
}
Heres some runs I did:
Product (193 lines) + full run of the code above = Internal Server Error + the whole site become under Internal Server Error whenever trying to access other page
Product (193 lines) + less the Email Block = Successfull
Product (18,000 lines) + full run of the code above = Internal Server Error + the whole site become under Internal Server Error whenever trying to access other page.
Product (18,000 lines) + less the Email Block = Internal Server Error + the whole site become under Internal Server Error whenever trying to access other page.
I don't know if it just me or what, but even the server returns internal server error, the products are keep adding on the database (I look at it and try to query a count and it increments) and stops at random point, that point the site is become accessible again. But sometime it doesnt do that.
Any ideas? Thanks in advance.
EDIT :
NID & PID is BIGINT, ISREAD is BOOLEAN, the rest are LONGTEXT
Plus while running, the page is /uploadpcn.php, this code is under /do_upload_pcn.php
so the scenario is that, the whole process is in loading while on /uploadpcn.php and when the process ends, the browser will go to /do_upload_pcn.php showing all echos OR shows internal server errors anytime in the process.

Answer 1

Try to log the loop with each record and you may come to know which particular record is causing the error. You may also apply some try-catch logic. I presume this could be a parsing error.
Another thing to notice is that your first INSERT query does not contains single-quotes around the string data. This could be another issue leading to the error.
Edit:
This query in the code in the question $query = sprintf('INSERT INTOread_details(NID,PID,ISREAD) VALUES(%s,%s,1);',$NID,$row['id']); should be like:
$query = sprintf('INSERT INTO `read_details` (`NID`, `PID`, `ISREAD`) VALUES (\'%s\', \'%s\', 1);', $NID, $row['id']);
I would suggest to use double quotes for constructing queries so that you may easily use single quotes for parameters.