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Asked: 2026-06-13T20:15:57+00:00

I have written a code in php where I: Open a txt file, Read

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I have written a code in php where I:

  1. Open a txt file,
  2. Read each line,
  3. Use the explode() function to break the line into pieces (Based on spaces)
  4. Assign each substring to variables and
  5. Insert everything in the database.

On these lines I have numbers and sometimes NULL values. The problem is that when I insert everything to mysql the null values are presented as 0 instead of null.

Is it possible to display the null values from the txt as.. null values in my table in db?

Please let me know if I didn’t explain something clear.

Thank you.
d.

<!DOCTYPE HTML>
<?php

// This code:
// 1) opens a txt file, which is stored in a specified folder,
// 2) reads each line of the file,
// 3) inserts the data in the specified database


// Connect to the database
include('connect.php'); 
// Define the location of the txt file.
$myFile = "/Applications/MAMP/htdocs/php_test/data_correct.txt";
// Open the file
$fh = fopen($myFile,'r') or die ("Could not open:".mysql_error());
// !feof means "not the end of the file"
while (!feof($fh)){
// fgets: gets the first line of $fh and assigns it to the variable $line
// Each line can be up to 5000 characters long
$line = fgets($fh,5000);
 // explode function separated the string by means of "tab" space
  list($WN,$TOW,$Receiver_ID,$lat,$lon,$height,$SVID,$Azimuth,$Elevation,$Total_S4_L1,$SNR_L1,$Phi01_L1,$Phi03_L1,$Phi10_L1,$Phi30_L1,$Phi60_L1,$TEC_TOW_45,$dTEC_TOW_60_45,$TEC_TOW_30,$dTEC_TOW_45_30,$TEC_TOW_15,$dTEC_TOW_30_15,$TEC_TOW,$dTEC_TOW_15_TOW,$L1_lock_time,$L2_lock_time,$SI_index_L1,$Total_S4_L2,$SNR_L2,$Phi01_L2,$Phi03_L2,$Phi10_L2,$Phi30_L2,$Phi60_L2,$Lock_L2,$SI_index_L2,$Total_S4_L5,$SNR_L5,$Phi01_L5,$Phi03_L5,$Phi10_L5,$Phi30_L5,$Phi60_L5,$Lock_L5,$SI_index_L5)=explode(" ",$line);

  // insert data into table in database. The name of the table is GPS.
 // The primary key increases automatically. The null values are acceptable.

    $query = ("INSERT INTO GPS      (WN,TOW,Receiver_ID,lat,lon,height,SVID,Azimuth,Elevation,Total_S4_L1,SNR_L1,Phi01_L1,Phi03_L1,Phi10_L1,Phi30_L1,Phi60_L1,TEC_TOW_45,dTEC_TOW_60_45,TEC_TOW_30,dTEC_TOW_45_30,TEC_TOW_15,dTEC_TOW_30_15,TEC_TOW,dTEC_TOW_15_TOW,L1_lock_time,L2_lock_time,SI_index_L1,Total_S4_L2,SNR_L2,Phi01_L2,Phi03_L2,Phi10_L2,Phi30_L2,Phi60_L2,Lock_L2,SI_index_L2,Total_S4_L5,SNR_L5,Phi01_L5,Phi03_L5,Phi10_L5,Phi30_L5,Phi60_L5,Lock_L5,SI_index_L5)  
     VALUES   ('".$WN."','".$TOW."','".$Receiver_ID."','".$lat."','".$lon."','".$height."','".$SVID."','".$Azimuth."','".$Elevation."','".$Total_S4_L1."','".$SNR_L1."','".$Phi01_L1."','".$Phi03_L1."','".$Phi10_L1."','".$Phi30_L1."','".$Phi60_L1."','".$TEC_TOW_45."','".$dTEC_TOW_60_45."','".$TEC_TOW_30."','".$dTEC_TOW_45_30."','".$TEC_TOW_15."','".$dTEC_TOW_30_15."','".$TEC_TOW."','".$dTEC_TOW_15_TOW."','".$L1_lock_time."','".$L2_lock_time."','".$SI_index_L1."','".$Total_S4_L2."','".$SNR_L2."','".$Phi01_L2."','".$Phi03_L2."','".$Phi10_L2."','".$Phi30_L2."','".$Phi60_L2."','".$Lock_L2."','".$SI_index_L2."','".$Total_S4_L5."','".$SNR_L5."','".$Phi01_L5."','".$Phi03_L5."','".$Phi10_L5."','".$Phi30_L5."','".$Phi60_L5."','".$Lock_L5."','".$SI_index_L5."')");



    $result = mysqli_query($dbcon, $query) or die('no available data');

   }// end of while loop
  fclose($fh); 

   ?>

The CREATE TABLE QUERY IS:

CREATE TABLE `GPS` ( 
  `id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
  `WN` INT,  # GPS Week Number
  `TOW` INT, # Time of Week (seconds)
  `Receiver_ID` VARCHAR( 30), # Name of GPS receiver
  `lat` FLOAT(10,6), # Latitude of the GPS receiver
  `lon` FLOAT(10,6), # Longitude of the GPS receiver
   `height` FLOAT(10,2), # Height
   `SVID` INT, #Satellite ID
   `Azimuth` INT, # Azimuth in degrees
   `Elevation` INT, #Elevation in degrees
   `Total_S4_L1` FLOAT(10,3), # Total S4 on L1 (dimensionless)
   `SNR_L1` FLOAT(10,1), # SNR on L1 (db)
   `Phi01_L1` FLOAT(10,3), # Phi01 on L1, 1-second phase sigma (radians)
   `Phi03_L1` FLOAT(10,3), # Phi03 on L1, 3-second phase sigma (radians)
   `Phi10_L1` FLOAT(10,3), # Phi10 on L1, 10-second phase sigma (radians)
   `Phi30_L1` FLOAT(10,3), # Phi30 on L1, 30-second phase sigma (radians)
   `Phi60_L1` FLOAT(10,3), # Phi60 on L1, 60-second phase sigma (radians)
   `TEC_TOW_45` FLOAT(10,4), # TEC at TOW -45s (TECU --> TEC SLUNT)
   `dTEC_TOW_60_45` FLOAT(10,4), # dTEC from TOW -60s to TOW -45s (TECU)
   `TEC_TOW_30` FLOAT(10,4), # TEC at TOW -30s (TECU --> TEC SLUNT)
  `dTEC_TOW_45_30` FLOAT(10,4), # dTEC from TOW -45s to TOW -30s (TECU)
   `TEC_TOW_15` FLOAT(10,4), # TEC at TOW -15s (TECU --> TEC SLUNT)
  `dTEC_TOW_30_15` FLOAT(10,4), # dTEC from TOW -30s to TOW -15s (TECU)
 `TEC_TOW` FLOAT(10,4), # TEC at TOW (TECU --> TEC SLUNT)
  `dTEC_TOW_15_TOW` FLOAT(10,4), # dTEC from TOW -15s to TOW (TECU)
  `L1_lock_time`  INT, # L1 lock time (seconds)
  `L2_lock_time` INT, #L2 lock time (seconds)
  `SI_index_L1` FLOAT (10,4), # SI Index on L1: (10*log10(Pmax)-  10*log10(Pmin))/(10*log10(Pmax)+10*log10(Pmin)) (dimensionless)
  `Total_S4_L2` FLOAT(10,3), # Total S4 on L2 (GPS/GLO) or E5a (GAL) (dimensionless)
   `SNR_L2` FLOAT(10,1), # SNR on L2 (dB)
  `Phi01_L2` FLOAT(10,3), # Phi01 on L2 (GPS/GLO) or E5a (GAL),  1-second phase sigma (radians)
   `Phi03_L2` FLOAT(10,3), # Phi03 on L2 (GPS/GLO) or E5a (GAL),  3-second phase sigma (radians)
   `Phi10_L2` FLOAT(10,3), # Phi10 on L2 (GPS/GLO) or E5a (GAL), 10-second phase sigma (radians)
   `Phi30_L2` FLOAT(10,3), # Phi30 on L2 (GPS/GLO) or E5a (GAL), 30-second phase sigma (radians)
   `Phi60_L2` FLOAT(10,3), # Phi60 on L2 (GPS/GLO) or E5a (GAL), 60-second phase sigma (radians)
  `Lock_L2`  INT, # Lock time of L2 (GPS/GLO) or E5a (GAL) (seconds)
  `SI_index_L2` FLOAT (10,4), # SI Index on L2 (GPS/GLO) or E5a (GAL) (dimensionless)
  `Total_S4_L5` FLOAT(10,3), # Total S4 on L5 (GPS/GLO) or E5a (GAL) (dimensionless)
 `SNR_L5` FLOAT(10,1), # SNR on L5 (dB)
 `Phi01_L5` FLOAT(10,3), # Phi01 on L5 (GPS/GLO) or E5a (GAL),  1-second phase sigma (radians)
  `Phi03_L5` FLOAT(10,3), # Phi03 on L5 (GPS/GLO) or E5a (GAL),  3-second phase sigma (radians)
   `Phi10_L5` FLOAT(10,3), # Phi10 on L5 (GPS/GLO) or E5a (GAL),  10-second phase sigma (radians)
  `Phi30_L5` FLOAT(10,3), # Phi30 on L5 (GPS/GLO) or E5a (GAL),  30-second phase sigma (radians)
  `Phi60_L5` FLOAT(10,3), # Phi60 on L5 (GPS/GLO) or E5a (GAL),  60-second phase sigma (radians)
  `Lock_L5`  INT, # Lock time of L5 (GPS/GLO) or E5a (GAL) (seconds)
  `SI_index_L5` FLOAT (10,4) # SI Index on L5 (GPS/GLO) or E5a (GAL) (dimensionless)
 ) # Default storage engine from version MySQL 5.5 is InnoDB
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1 Answer

  1. Editorial Team

    To pass a NULL to MySQL, you do just that.

    INSERT INTO table (field,field2) VALUES (NULL,'value')

    In the code, check if $var, $var2 are null, if they are, use NULL instead of ‘$var’ or ‘$var2’.

    $var = !empty($var) ? "'$var'" : "NULL";
$var2 = !empty($var2) ? "'$var2'" : "NULL";

$query = "INSERT INTO data (field1, field2)
      VALUES ('$var', '$var2',)";
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