Read file lines backwards (fgets) with php - php

Question

I have a txt file that I want to read backwards, currently I'm using this:
$fh = fopen('myfile.txt','r');
while ($line = fgets($fh)) {
echo $line."<br />";
}
This outputs all the lines in my file.
I want to read the lines from bottom to top.
Is there a way to do it?

Answer 1

First way:
$file = file("test.txt");
$file = array_reverse($file);
foreach($file as $f){
echo $f."<br />";
}
Second Way (a):
To completely reverse a file:
$fl = fopen("\some_file.txt", "r");
for($x_pos = 0, $output = ''; fseek($fl, $x_pos, SEEK_END) !== -1; $x_pos--) {
$output .= fgetc($fl);
}
fclose($fl);
print_r($output);
Second Way (b):
Of course, you wanted line-by-line reversal...
$fl = fopen("\some_file.txt", "r");
for($x_pos = 0, $ln = 0, $output = array(); fseek($fl, $x_pos, SEEK_END) !== -1; $x_pos--) {
$char = fgetc($fl);
if ($char === "\n") {
// analyse completed line $output[$ln] if need be
$ln++;
continue;
}
$output[$ln] = $char . ((array_key_exists($ln, $output)) ? $output[$ln] : '');
}
fclose($fl);
print_r($output);

Answer 2

Try something simpler like this..
print_r(array_reverse(file('myfile.txt')));

Answer 3

Here is my solution for just printing the file backwards. It is quite memory-friendly. And seems more readable (IMO [=in my opinion]).
It goes through the file backwards, count the characters till start of a line or start of the file and then reads and prints that amount of characters as a line, then moves cursor back and reads another line like that...
if( $v = #fopen("PATH_TO_YOUR_FILE", 'r') ){ //open the file
fseek($v, 0, SEEK_END); //move cursor to the end of the file
/* help functions: */
//moves cursor one step back if can - returns true, if can't - returns false
function moveOneStepBack( &$f ){
if( ftell($f) > 0 ){ fseek($f, -1, SEEK_CUR); return true; }
else return false;
}
//reads $length chars but moves cursor back where it was before reading
function readNotSeek( &$f, $length ){
$r = fread($f, $length);
fseek($f, -$length, SEEK_CUR);
return $r;
}
/* THE READING+PRINTING ITSELF: */
while( ftell($v) > 0 ){ //while there is at least 1 character to read
$newLine = false;
$charCounter = 0;
//line counting
while( !$newLine && moveOneStepBack( $v ) ){ //not start of a line / the file
if( readNotSeek($v, 1) == "\n" ) $newLine = true;
$charCounter++;
}
//line reading / printing
if( $charCounter>1 ){ //if there was anything on the line
if( !$newLine ) echo "\n"; //prints missing "\n" before last *printed* line
echo readNotSeek( $v, $charCounter ); //prints current line
}
}
fclose( $v ); //close the file, because we are well-behaved
}
Of course replace PATH_TO_YOUR_FILE with your own path to your file, # is used when opening the file, because when the file is not found or can't be opened - warning is raised - if you want to display this warning - just remove the error surpressor '#'.

Answer 4

If the file is not so big you can use file():
$lines = file($file);
for($i = count($lines) -1; $i >= 0; $i--){
echo $lines[$i] . '<br/>';
}
However, this requires the whole file to be in memory, that's why it is not suited for really large files.

Answer 5

Here's my simple solution without messing up anything or adding more complex code
$fh = fopen('myfile.txt','r');
while ($line = fgets($fh)) {
$result = $line . "<br>" . $result;
}
echo $result // or return $result if you are using it as a function