how to insert into database columns one after the other using php - php

Question

I have three columns that I want to insert data into using php. the code will be run three times.
I want if run the code the first time to insert only on column1 while leaving other columns empty.
If run the second time to insert into only column2 while leaving other column empty
and so on. I have tried the code below but cannot get it to work. it only inserts into the column1
<?php
error_reporting(0);
include('db.php');
$result = $db->prepare('SELECT * FROM rec');
$result->execute(array());
while ($row = $result->fetch())
{
//$id = $row['id'];
$column1 = $row['column1'];
$column2 = $row['column2'];
$column3 = $row['column3'];
}
if ($column1 ==''){
echo 'empty';
$statement = $db->prepare('INSERT INTO rec(column1)
values(:column1)');
$statement->execute(array(':column1' =>'$column1'));
} elseif ($column2 ==''){
echo 'empty2';
$statement = $db->prepare('INSERT INTO rec (column2)
values(:column2)');
$statement->execute(array(':column2' =>'$column2'));
} elseif ($column3==''){
echo 'empty3';
$statement = $db->prepare('INSERT INTO rec(column3)
values(:column3)');
$statement->execute(array(':column3' =>'$column3'));
}

Answer 1

Firstly it is not a proper way of designing database.
Secondly, use if statements only rather than nested if-else statements and it will work!

Answer 2

Your if-else is such that the correct data is not getting inserted properly . Use the following code which will solve your purpose in your way . However , the way you are following is not correct . Either you follow the conventional way to create a database and inserting values into it or use dynamic fields for a table and insert it another way .
if ($column1 ==''){
echo 'empty';
}
else{
$statement = $db->prepare('INSERT INTO rec(column1)
values(:column1)');
$statement->execute(array(':column1' =>'$column1'));
}
if ($column2 ==''){
echo 'empty2';
}
else{
$statement = $db->prepare('INSERT INTO rec (column2)
values(:column2)');
$statement->execute(array(':column2' =>'$column2'));
}
if ($column3==''){
echo 'empty3';
}
else{
$statement = $db->prepare('INSERT INTO rec(column3)
values(:column3)');
$statement->execute(array(':column3' =>'$column3'));
}