Using PHP to display items on page - php

Question

I have a document called subjects.txt in the following format:
DateCreated,Subject,Link
18.10.2015,"Math",http: //address.html
17.10.2015,"English",http: //address.html
18.10.2015,"English",http: //address.html
19.10.2015,"Science",http: //address.html
17.10.2015,"Math",http: //address.html
The file contains URLs of sites created based on a school subject. There can be more than one site for a subject.
The goal is to use PHP to open, read, and display the contents of the file in the following format:
Math
Link 1
Link 2
English
Link 1
Link 2
Science (because there's only one link, the name of the subject is the
link)
So far I've been able to open and read the file:
$file = "./subjects.txt";
$subjects = file_get_contents($file);
I'm having trouble trying to determine how to go about writing the file in specified format.
I've tried using explode to separate the elements with "," - however I don't know where to go from there.

Answer 1

Your input file looks to be in Comma-separated values (CSV) format. PHP has a built-in fgetcsv function designed to make reading CSV data from a file easy.
<?php
$file = './subjects.txt';
$fh = fopen($file, 'r');
if ($fh === false) {
die("Can not read {$file}");
}
$data = array();
while (($row = fgetcsv($fh, 1000, ',')) !== false) {
if ($row[0] === 'DateCreated') {
// Ignore the column header row
continue;
}
list($date, $subject, $link) = $row;
if (!isset($data[$subject])) {
$data[$subject] = array();
}
$data[$subject][] = $link;
}
fclose($fh);
foreach ($data as $subject => $links) {
// TODO: output each subject here
}

Answer 2

Here is another version
<?php
$file = "./subjects.txt";
$h = fopen($file, "r");
if($h !== false) {
$subjects = [];
$data = [];
while(!feof($h)) {
if($line = trim(fgets($h))) {
$line = explode(",", $line);
if(!in_array("DateCreated",$line)) {
array_push($subjects, $line);
}
}
}
fclose($h);
foreach ($subjects as $subject) {
if(!isset($data[$subject[1]])) {
$data[$subject[1]] = [];
}
$data[$subject[1]][] = $subject[2];
}
foreach ($data as $subject => $links) {
if(count($links) == 1) {
echo "<p>$subject</p>\n";
} else {
$i = 1;
echo "<p>$subject</p>\n";
echo "<ul>\n";
foreach ($links as $link) {
echo "<li>link$i</li>\n";
$i++;
}
echo "</ul>\n";
}
}
}
?>

Answer 3

The problem using file_get_contents() is that retrieves all the file contents into $subjects.
You have to use a different approach. For example fgets():
$fp = fopen("./subjects.txt", "r");
if ($fp){
while (($line = fgets($fp)) !== false){
// So here you can treat each line individually.
// You can use explode (";", $line) for example if the line is not empty
}
}
fclose($fp);
Using fgets() will allow you to parse each of the file's lines individually.

Answer 4

As stated doing this with a database would be much easier probably 3 lines of code. Here's one approach you could use though.
$data = '18.10.2015,"Math",http: //address.html
17.10.2015,"English",http: //address1.html
18.10.2015,"English",http: //address2.html
19.10.2015,"Science",http: //address3.html
17.10.2015,"Math",http: //address4.html';
preg_match_all('~^(.*?),"(.*?)",(.*?)$~m', $data, $fields);
array_multisort($fields[2], SORT_STRING, $fields[1], $fields[3]);
$lastcat = '';
foreach($fields[2] as $key => $cat) {
if($cat != $lastcat) {
echo $cat . "\n";
}
$lastcat = $cat;
echo $fields[3][$key] . "\n";
}
Output:
English
http: //address1.html
http: //address2.html
Math
http: //address4.html
http: //address.html
Science
http: //address3.html
The array_multisort is how the categories are grouped.
Here's a regex101 demo of what that regex is doing. https://regex101.com/r/wN3nB2/1
Update for single record check (only ran 1 test on it):
$data = '18.10.2015,"Math",http: //address.html
17.10.2015,"English",http: //address1.html
18.10.2015,"English",http: //address2.html
19.10.2015,"Science",http: //address3.html
17.10.2015,"Math",http: //address4.html';
preg_match_all('~^(.*?),"(.*?)",(.*?)$~m', $data, $fields);
array_multisort($fields[2], SORT_STRING, $fields[1], $fields[3]);
$lastcat = '';
foreach($fields[2] as $key => $cat) {
if((empty($fields[2][($key +1)]) && $cat != $lastcat)|| ($cat != $lastcat && !empty($fields[2][($key +1)]) && $fields[2][($key +1)] != $cat)) {
//single record
echo $cat . $fields[3][$key] . "\n";
} else {
if($cat != $lastcat) {
echo $cat . "\n";
}
$lastcat = $cat;
echo $fields[3][$key] . "\n";
}
}