PHP file write - max lines - php

Question

How to put a limit for writing in a file, if it hit the limit then remove the last line..
As example here's a file:
Line 3
Line 2
Line 1
i want to max line it for 3 lines only.. so when i write a new line using any append functions it removes the last line.. Let's say i just wrote a new line ( Line 4 ).. so it goes to the last one and remove it, result should be :
Line 4
Line 3
Line 2
And for a new written line (Line 5):
Line 5
Line 4
Line 3
numeric lines is not required, i just want to remove the last line if there's a new added line via an append functions (file_put_contents / fwrite) and max it by 3 or a specific number i give

Answer 1

You can try
$max = 3;
$file = "log.txt";
addNew($file, "New Line at : " . time());
Function Used
function addNew($fileName, $line, $max = 3) {
// Remove Empty Spaces
$file = array_filter(array_map("trim", file($fileName)));
// Make Sure you always have maximum number of lines
$file = array_slice($file, 0, $max);
// Remove any extra line
count($file) >= $max and array_shift($file);
// Add new Line
array_push($file, $line);
// Save Result
file_put_contents($fileName, implode(PHP_EOL, array_filter($file)));
}

Answer 2

Here's one way:
Use file() to read the file's lines into an array
Use count() to determine if there's more than 3 elements in the array. If so:
Remove the last element of the array with array_pop()
Use array_unshift() to add an element (the new line) to the front of the array
Overwrite the file with the lines of the array
Example:
$file_name = 'file.txt';
$max_lines = 3; #maximum number of lines you want the file to have
$new_line = 'Line 4'; #content of the new line to add to the file
$file_lines = file($file_name); #read the file's lines into an array
#remove elements (lines) from the end of the
#array until there's one less than $max_lines
while(count($file_lines) >= $max_lines) {
#remove the last line from the array
array_pop($file_lines);
}
#add the new line to the front of the array
array_unshift($file_lines, $new_line);
#write the lines to the file
$fp = fopen($file_name, 'w'); #'w' to overwrite the file
fwrite($fp, implode('', $file_lines));
fclose($fp);

Answer 3

Try this.
<?php
// load the data and delete the line from the array
$lines = file('filename.txt');
$last = sizeof($lines) - 1 ;
unset($lines[$last]);
// write the new data to the file
$fp = fopen('filename.txt', 'w');
fwrite($fp, implode('', $lines));
fclose($fp);
?>

Answer 4

Modified from Baba's answer; this code will write the new line at the beginning of the file and will errase the last one to keep always 3 lines.
<?php
function addNew($fileName, $line, $max) {
// Remove Empty Spaces
$file = array_filter(array_map("trim", file($fileName)));
// Make Sure you always have maximum number of lines
$file = array_slice($file, 0, --$max);
// Remove any extra line and adding the new line
count($file) >= $max and array_unshift($file, $line);
// Save Result
file_put_contents($fileName, implode(PHP_EOL, array_filter($file)));
}
// Number of lines
$max = 3;
// The file must exist with at least 2 lines on it
$file = "log.txt";
addNew($file, "New Line at : " . time(), $max);
?>