How do I edit this text file using PHP?

I do have a text file having around 400k data in it. and its content is like this..

1,james
2,mathew
3,yancy
4,brandon
5,molner
6,nick
7,neil...and so on

How do I remove numbers and comas from this text file and keep only names?

Read the file into an array, where each array item is one line. Walk throught the array, find the first comma, and remove it and everything before. Then write it all back out again.

// Warning! Brain-compiled code ahead.

$arr = file('myfile.txt');
foreach ( $arr as &$val )
    $val = substr($val, strpos($val, ',') + 1);
file_put_contents('myoutfile.txt', implode(PHP_EOL, $arr));

Note - no error checking. If a line lacks a comma, or comma is the last character, chaos ensues.

400k isn't incredibly much, so you should get away with this (tested):

foreach (file($path) as $line)
    print preg_replace("~^[0-9]+\,(.*)~", "$1", $line);

Here is a perl one liner that do the job:

perl -i.save -pe 's/^\d+,//'  test.txt

The original file will be saved in test.txt.save

This is tested and will return it as a list but you can save it to a database if you want:

$file_path='my_file.txt';
$file_handler = fopen($file_path, 'rt');

$doc = fread($file_handler, filesize($file_path)+1);

$rows = explode("\n", $doc);
$rows_array = array();
foreach ($rows as $row) {
    $data = explode(",", $row);
        $return_array[] = $data[1];
}

//print_r($return_array);
    //you can save it to a db

echo '<ul>';
foreach($return_array as $value){
    echo '<li>'.$value.'</li>';
}   
echo '</ul>';