How to delete a line from the file with php?

I have a file named $dir and a string named $line, I know that this string is a complete line of that file but I don't know its line number and I want to remove it from file, what should I do?

Is it possible to use awk?

Read the lines one by one, and write all but the matching line to another file. Then replace the original file.

$contents = file_get_contents($dir);
$contents = str_replace($line, '', $contents);
file_put_contents($dir, $contents);

this will just look over every line and if it not what you want to delete, it gets pushed to an array that will get written back to the file. see this

 $DELETE = "the_line_you_want_to_delete";

 $data = file("./foo.txt");

 $out = array();

 foreach($data as $line) {
     if(trim($line) != $DELETE) {
         $out[] = $line;
     }
 }

 $fp = fopen("./foo.txt", "w+");
 flock($fp, LOCK_EX);
 foreach($out as $line) {
     fwrite($fp, $line);
 }
 flock($fp, LOCK_UN);
 fclose($fp);  

It can be solved without the use of awk:

function remove_line($file, $remove) {
    $lines = file($file, FILE_IGNORE_NEW_LINES);
    foreach($lines as $key => $line) {
        if($line === $remove) unset($lines[$key]);
    }
    $data = implode(PHP_EOL, $lines);
    file_put_contents($file, $data);
}