Remove a line from file if it exists - php

Question

I'm getting used to PHP and trying to remove a line from a file (if it exists) and resave the file.
So if I had the file
user1
user2
user3
user4
I could use
if(existsAndRemove("user3")){
do thing
}
I've tried using code similar to the code below but it sometimes bugs out and will only remove a line if it is last in the file. I have no idea how to fix this.
$data2 = file("./ats.txt");
$out2 = array();
foreach($data2 as $line2) {
if(trim($line2) != $acc) {
$out2[] = $line2;
}
}
$fp2 = fopen("./ats.txt", "w+");
flock($fp2, LOCK_EX);
foreach($out2 as $line2) {
fwrite($fp2, $line2);
}
flock($fp2, LOCK_UN);
fclose($fp2);
}
}
Any help at all would be greatly appreciated, and i would also appreciate if you could explain the code too so I could easier learn from it!!
Thank you.

Answer 1

If the file size is small enough that you're not worried about reading it all into memory, you could do something more functional
// Read entire file in as array of strings
$data = file("./ats.txt");
// Some text we want to remove
$acc = 'user3';
// Filter out any lines that match $acc,
// ignoring any leading or trailing whitespace
//
$filtered_data = array_filter(
$data,
function ($line) use ($acc) {
return trim($line) !== $acc;
}
)
// If something changed, write the file back out
if ($filtered_data !== $data) {
file_put_contents('./ats.txt', implode('', $filtered_data));
}

Answer 2

Something like this might work:
function remove_user($user) {
$file_path = "foo.txt"
$users = preg_split("[\n\r]+", file_get_contents($file_path));
foreach ($users as $i => $existing) {
if ($user == $existing) {
$users = array_splice($users, $i, 1);
file_put_contents($file_path, implode("\n", $users));
break;
}
}
}

Answer 3

Should be much easier since you're already using file():
$data2 = file("./ats.txt", FILE_IGNORE_NEW_LINES);
unset($data2[array_search('user3', $data2)]);
file_put_contents("./ats.txt", implode("\n", $data2));
Or to check if it exists first:
$data2 = file("./ats.txt", FILE_IGNORE_NEW_LINES);
if( ($key = array_search('user3', $data2)) !== false ) {
unset($data2[$key]);
file_put_contents("./ats.txt", implode("\n", $data2));
}