PHP File: Inserting Lines into a File

PHP Array Tips - Part 14: Like removing line from file, with little trick in array, we can insert lines into file. Just read into array, insert element to array, then write back to file.

<?php
$f = "test.txt";

// read into array
$arr = file($f);

// add second line
array_splice($arr,1,0, array("test line 2\r\n"));

// reindex array
$arr = array_values($arr);

// write back to file
file_put_contents($f,implode($arr));
?>