<?php
$str = <<<EOL
1<>挨拶<><>2/9<>1
2<>挨拶<><>2/9<>0
3<>謝罪<><>2/22<>1
4<>挨拶<><>3/21<>0
5<>お礼<><>4/1<>1
EOL;

$lines = explode("\n", $str);

foreach ($lines as $line) {
     $items[] = explode("<>", $line);
}

foreach ($items as $item) {
     $result .= $item[0] . "\n";
}

file_put_contents('log.txt', $result);