Value of previous row in CSV import via PHP

Question

I'm importing data from a CSV via PHP.

On some lines of the CSV, column 1 has a value, and on other lines it does not have a value. Column 2 always has a value.

If column 1 is empty and column 2 has a value, I would like column 1 to use the previous value in column 1. For example

|-------|-------|
| Col 1 | Col 2 |
|-------|-------|
|   A   |   2   |
|   B   |   5   |
|   C   |   3   |
|       |   1   |
|   D   |   7   |

Would return

 A2 
 B5
 C3
 C1
 D7

I can use prev() on an array, but as $data[0] is a string I can't use prev()

while (($data = fgetcsv($handle, 1000, ",")) !== FALSE) {
    if ($i > 0) {  
            if ($data[0]=='' && $data[1]!=='') { 
            echo prev($data[0]).$data[1]'<br/>';
            } else { 
            echo $data[0].$data[1]'<br/>';
            }
        }
    $i++;
}

Banging my head against a wall for hours now, so I'd love a pointer!

Simply stash the value of column one and use it if you find it blank on a line. — Dave
– Dave, Commented May 1, 2018 at 12:31

caramba · Accepted Answer · 2018-05-01 12:31:47Z

1

This should work as long as the first row is not empty...

$x = null;
while (($data = fgetcsv($handle, 1000, ",")) !== FALSE) {
    if ($i > 0) {
            $x = $data[0] == '' ? $x : $data[0];
            // this is like: if $data[0] is empty then use $x else say $x is $data[0].
            // Like that you can keep track of the previous value.
            // If there is one overwrite with the new one else keep the old value
            echo $x.$data[1]'<br/>';
        }
    $i++;
}

answered May 1, 2018 at 12:31

caramba

22.5k20 gold badges94 silver badges134 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

charliechina Over a year ago

Thanks Caramba. I tried that before but had been storing the variable inside the while loop!

caramba Over a year ago

@charliechina no worries, that happens to all of us once. happy coding

Funk Forty Niner · Accepted Answer · 2018-05-01 12:33:48Z

1

You can store previous value in the variable and use that

$previousColumn1 = '';
while (($data = fgetcsv($handle, 1000, ",")) !== FALSE) {
    if ($i > 0) {  
            if ($data[0]=='' && $data[1]!=='') { 
            echo $previousColumn1.$data[1]'<br/>';
            } else { 
            $previousColumn1 = $data[0];
            echo $data[0].$data[1]'<br/>';
            }
        }
    $i++;
}

edited May 1, 2018 at 12:33

Funk Forty Niner

74.2k14 gold badges71 silver badges146 bronze badges

answered May 1, 2018 at 12:32

Aman jaura

2013 silver badges15 bronze badges

Comments

Nigel Ren · Accepted Answer · 2018-05-01 12:40:58Z

0

As has been mentioned, just storing the previous value and overwriting it any time a new value is given will do the job. It will assume that if the first row is blank that the $prev value you provide outside the loop will be used...

$prev = '';
while (($data = fgetcsv($handle, 1000, ",")) !== FALSE) {
    $prev = $data[0]?:$prev;
    echo $prev.$data[1].PHP_EOL;
}

This uses the short form of ?: to say if there is a value for $data[0] - then use it, otherwise use $prev.

answered May 1, 2018 at 12:40

Nigel Ren

57.3k11 gold badges49 silver badges59 bronze badges

Collectives™ on Stack Overflow

Value of previous row in CSV import via PHP

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related