PHP: Reading specific csv lines into a two-dimensional array

Question

I have a file arranged like so:
"url1","info1"
"url2","info2"
"url3","info3" ... all the way up to "url15","info15"

I would like to read the last 10 lines of the file into an array such that $pagelist[0][0] would give url5 and $pagelist[0][1] would give info5.

My current code is as follows:

$file=fopen(csvfile.txt,"r");
$pagelist=array();
$i=0;
$key=0;
while (!feof($file)) {
    if ($i >= (count($file)-11)) {
        $pagelist[$key]=fgetcsv($file);
        $key++; }
    $i++;
}
fclose($file)

When I used print_r($pagelist) it seemed to have loaded all the lines of the file into the array instead of just the last 10. Can anyone see what I've done wrong in my code? thanks :)

Stephen Ó Connor · Accepted Answer · 2016-09-29 11:05:42Z

3

The problem with you code is that count($file) is not doing what you think. $file is just a file handle resource, not an array. You end up comparing $i >= -11, which will of course always evaluate to true/

You might try something like this if you want to just use linux to grab the last ten lines (not sure if you are on linux):

$initial_csv = 'csvfile.txt';
$truncated_csv ='csvfile_trun';
$number_of_lines_from_end = 10;
shell_exec('tail -n ' . $number_of_lines_from_end . ' ' . $initial_csv . ' > ' . $truncated_csv);
$file=fopen($truncated_csv,"r");
$pagelist=array();
$i=0;
while (!feof($file)) {
    $pagelist[$i]=fgetcsv($file);
    $i++;
}
fclose($file)

Alternatively, if you don't mind having the entire file in memory (i.e. the file will remain small), you can read the entire file into an array like this.

$csv = 'csvfile.txt';
$number_of_lines_from_end = 10;
$file_array = file($csv);
$line_count = count($file_array);
$start = $line_count - $number_of_lines_from_end - 1;
$pagelist=array();
for ($i = $start; $i < $line_count; $i++) {
    $pagelist[]=fgetcsv($file);
}

edited Sep 29, 2016 at 11:05

Stephen Ó Connor

3856 silver badges22 bronze badges

answered Dec 15, 2012 at 0:12

Mike Brant

71.4k10 gold badges102 silver badges104 bronze badges

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

8 Comments

Wrikken Over a year ago

If going the file() route (huge memory indeed), an foreach(array_slice($file_array,$line_count-11,10) as $line) $pagelist[]=str_getcsv($line); seems more apt.

Mike Brant Over a year ago

@Wrikken The only reason I provided the file() solution is that it seems the OP is dealing with relatively little data. If you were talking about thousands of line of data, I would use something like the linux tail command to solution to just get the portion of the data is cared about right up front. You are right that array_slice() would work fine just as well.

ernie Over a year ago

Just to clarify, the array_slice doesn't address the memory issue; the use of file() means that the file is already read into memory. array_slice just avoids looping through the first n-10 lines.

Mike Brant Over a year ago

@ernie You are correct about the memory consumption. The code shown does not loop through the first n-10 lines, however.

Wrikken Over a year ago

Yes, I wouldn't advocate file() for a couple of MBs of logfiles for instance, I was just saying that if we have it, we might as well use it (and your code misses a seeking to the proper line in that part b.t.w.). If I was the OP, I'd go for the tail solution most definitely (with proper escapeshellarg for dynamic arguments).

|

Wrikken · Accepted Answer · 2012-12-15 00:34:54Z

0

Yet another implementation, for the fun of it (Mike's tail is probably fastest):

$storage  = new SPLFixedArray(10);
$i = 0;
while(($line = fgets($file)) && ++$i) {
    $storage[$i%10] = $line;
}
$storage = $storage->toArray();
//switch if order is important;
$prepend = array_splice($storage,($i%10)+1,10 - ($i%10));
array_splice($storage,0,0,$prepend);
//interpret csv
$result = array_map('str_getcsv',$storage);

answered Dec 15, 2012 at 0:34

Wrikken

70.8k8 gold badges99 silver badges136 bronze badges

1 Comment

Wrikken Over a year ago

FWIW, a simple 1M lines seems to take about 2 seconds here. Fast enough for shell scripts / crons, waaaaaay to long for HTTP requests.

bobthyasian · Accepted Answer · 2012-12-15 00:13:39Z

-1

$file=fopen(csvfile.txt,"r");    
$pagelist= [];                  
$temp = fgetcsv($file);          
array_merge($pagelist, $temp);   
fclose($file);                              
print_r($pagelist);                         
$lastten = array_slice($pagelist, -10, 10); 
print_r($lastten);

*I might be wrong about the slice offset and limit.

answered Dec 15, 2012 at 0:13

bobthyasian

9436 silver badges17 bronze badges

1 Comment

Mike Brant Over a year ago

You need a loop for fgetcsv as it reads only a single line from the file.

Collectives™ on Stack Overflow

PHP: Reading specific csv lines into a two-dimensional array

3 Answers 3

8 Comments

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

8 Comments

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related