Array isn't sorting when writing to file - php

Question

I wrote this script:
<?PHP
$file_handle = fopen("info.txt", "rb");
while (!feof($file_handle) ) {
$line_of_text = fgets($file_handle);
$parts[] = explode('|', $line_of_text);
}
fclose($file_handle);
$a = $parts;
function cmp($a,$b){
return strtotime($a[8])<strtotime($b[8])?1:-1;
};
uasort($a, 'cmp');
$failas = "dinfo.txt";
$fh = fopen($failas, 'w');
for($i=0; $i<count($a); $i++){
$txt=implode('|', $a[$i]);
fwrite($fh, $txt);
}
fclose($fh);
?>
When I use:
print_r($a);
after
uasort($a, 'cmp');
Then I can see sorted array. But when I write to file using these commands:
$fh=fopen($failas, 'w');
for($i=0; $i<count($a); $i++){
$txt=implode('|', $a[$i]);
fwrite($fh, $txt);
}
fclose($fh);
It shows not sorted information, what am I doing wrong?

Answer 1

This should work for you:
Here I first get your file into an array with file() where every line is one array element. There I ignore empty lines and new line characters at the end of each line.
After this I sort the array with usort(). Where I first get all dates and times from each line by explode()'ing it. After this I simply get the timestamp of each date with strtotime() and compare it which each other.
At the end I simply save the file with file_put_contents(), where I also add a new line character at the end of each line with array_map().
<?php
$lines = file("test.txt", FILE_SKIP_EMPTY_LINES | FILE_IGNORE_NEW_LINES);
usort($lines, function($a, $b){
list($aDate, $aTime) = explode(" ", explode("|", $a)[substr_count($a, "|")]);
list($bDate, $bTime) = explode(" ", explode("|", $b)[substr_count($b, "|")]);
if(strtotime("$aDate $aTime") == strtotime("$bDate $bTime"))
return 0;
return strtotime("$aDate $aTime") < strtotime("$bDate $bTime") ? 1 : -1;
});
file_put_contents("test.txt", array_map(function($v){return $v . PHP_EOL;}, $lines));
?>
Side notes:
I would recommend you to save this data in a database where it is much flexible to sort and getting the data!
EDIT:
For people which have a php version (echo phpversion();) under <5.3, just change the anonymous functions to normal functions and pass the function name as strings like this:
<?php
$lines = file("test.txt", FILE_SKIP_EMPTY_LINES | FILE_IGNORE_NEW_LINES);
function timestampCmp($a, $b) {
$aExploded = explode("|", $a);
$bExploded = explode("|", $b);
list($aDate, $aTime) = explode(" ", $aExploded[substr_count($a, "|")]);
list($bDate, $bTime) = explode(" ", $bExploded[substr_count($b, "|")]);
if(strtotime("$aDate $aTime") == strtotime("$bDate $bTime"))
return 0;
return strtotime("$aDate $aTime") < strtotime("$bDate $bTime") ? 1 : -1;
}
function addEndLine($v) {
return $v . PHP_EOL;
}
usort($lines, "timestampCmp");
file_put_contents("test.txt", array_map("addEndLine", $lines));
?>