php find earliest date in the format dd/mm/yyyy in a text file

[increase]

I have a text file in the following format

03/12/2023 06 This is the text in the line
03/12/2023 06 This is the text in the line
03/12/2023 06 This is the text in the line
03/12/2023 06 This is the text in the line
22/11/2023 06 This is the text in the next line
22/11/2023 06 This is the text in the next line
03/11/2023 06 This is another text in the line
03/11/2023 06 This is another text in the line
03/11/2023 06 This is another text in the line
04/12/2023 06 This is yet another text in the line
04/12/2023 06 This is yet another text in the line

Which is read into an array $data, from this array, I want to output the earliest date which in this case would be 03/11/2023

[requinix]

What code have you tried so far and what happened when you ran it?

[Barand]

use usort() with a callback function which converts the first 10 chars of each line to yyyy-mm-dd format and compares them.

[Psycho]

$earliestDateTs = false;
foreach($data as $line)
{
	$dateStr = substr($line, 0, 10);  //Get just the date part of the string
	$dateTs  = strtotime($dateStr);   //Convert the date string to a timestamp
	if(!$earliestDateTs) { $earliestDateTs = $dateTs; }  //If earliestDateTs not set (i.e. first iteration) set to this line's timestamp
	$earliestDateTs = min($dateTs, $earliestDateTs);  //Set earliestDateTs to the minimum of the current value or this line's timestamp
}

echo "Earliest date: " . date('m/d/Y', $earliestDateTs);

 

[Barand]

Alternatively

usort($data, fn($a, $b) => isoDate($a) <=> isoDate($b));
echo $data[0];                                                        //--> 03/11/2023 06 This is another text in the line

function isoDate($text)
{
    $d = substr($text, 0, 10);
    return DateTime::createFromFormat('d/m/Y', $d)->format('Y-m-d');
}