Deleting/replacing data inside text file - php

Question

I want to do if conditional between text data and variable data then delete the line
Example
I have a txt data with usernames like ( one two one three one) every user in line,
And i want to delete all data except "one" username
My Code;
if(file_get_contents('visitors.txt') != "one") {
$GetLine = ;
function removeLine ($url, $lineToRemove)
{
$data = file_get_contents($url);
$lines = explode(PHP_EOL, $data);
$lineNo = 1;
foreach($lines as $line)
{
$linesArray[$lineNo] = $line;
$lineNo++;
}
unset($linesArray[$lineToRemove]);
return implode("\n", $linesArray);
}
$data = removeLine ("username.txt", $getLine);
echo $data
}
the function is used to remove lines.
My problem is doing if with the data + $getLine number, I just want to remove all the lines except line that has one word.

Answer 1

Can simply do it with a regular expression:
$file = preg_grep('#one#', file('file.txt'));
This will make $file an array holding only lines containing the string "one". To turn the array back into a string, you just implode it.
If you only want to echo the lines containing "one", you can also use iterators:
$file = new RegexIterator(new SplFileObject("file.txt"), '#one#');
foreach ($file as $content) {
echo $content, PHP_EOL;
}
This will go over the file line by line and echo any line having the string one in it. The benefit is that it doesn't use two arrays as intermediate structures.

Answer 2

Just a note, you shouldn't be defining functions inside an if statement.
Also, unless I'm misunderstanding, you shouldn't even need line numbers.
function remove_line( $data, $remove ){
$lines = explode( PHP_EOL, $data ); // Convert to Array
$new_lines = ''; // Start a new variable we'll add to in a loop
foreach( $lines as $line ){
$line = trim( $line ); // Trim Whitespace
if( $line != $remove ){
// Line isn't a line we want removed, so save it plus an EOL
$new_lines .= $line.PHP_EOL;
}
}
return $new_lines;
}
Now if you load in a file like so: $file = file_get_contents( 'my-file.txt' ); that contains the following:
One
Two
One
Three
One
Once you run it through the remove_line function, you'll end up something like:
$file = file_get_contents( 'my-file.txt' );
$new_file = remove_line( $file, 'One' );
var_dump( $new_file ); // Returns: string(10) "Two Three "