how to check if date and string exist in text file - php

Question

I have a php function to log users:
if(isset($_POST['enter'])){
if($_POST['name'] != "" && trim($_POST['name'])!= "" ){
$_SESSION['name'] = stripslashes(htmlspecialchars($_POST['name']));
$text_message = "<div class='msgln'><span class='chat-time'>".date("F j, g:i A")."</span> <b class='user-name'>".$_SESSION['name']."</b> </div>";
file_put_contents("users.html", $text_message, FILE_APPEND | LOCK_EX);
It's working fine, just if someone is refreshing the page, the "file_put_contents" function will log again.
So i'm trying to avoid duplicates:
$chck = file_get_contents("users.html");
if (false === strpos($chck, date("F j, g").' '.$_SESSION['name']){
//file_put_contents
}
I want to check for date - only date and hour (not minutes) and the username. As i'm using 12h time, how can i check for PM and AM ?
Output:
January 18, 7:33 AM username
January 18, 7:41 AM username
January 18, 7:45 AM username
For simplifying: i want to check for "January 18," "7" "AM" "username".

Answer 1

The sequence date("F j, g").' '.$_SESSION['name'] cannot exists, because there are some characters between the date and the user name.
You could check use a simple regular expression like "January 18, 9:[0-9]{2} AM"
$date = date('F j, g:[0-9]{2} A');
$match = preg_match('~' . $date . '~', $text_message);
if (strpos($text_message, $_SESSION['name']) === false && !$match) {
echo "match not found";
// file_put_contents()
}
else {
echo "match found";
}

Answer 2

I think it is hard to do that since your date is string ( not stored in a database ), in less words you can't get the date String to compare if it is already inserted, because if you have for example these inputs in users.html:
<div class='msgln'><span class='chat-time'>January 18, 7:00 AM</span> <b class='user-name'>evara</b> </div>
<div class='msgln'><span class='chat-time'>January 18, 7:31 AM</span> <b class='user-name'>Know-nothing</b> </div>
and then you got an request to insert new user, so you need to check if the user already had been inserted with
username = "evara" && date = January 18, 7:01 AM
so then you can't compare them. but why not comparing if just username was already inserted ?
if (false === strpos($chck,$_SESSION['name']){
//file_put_contents
}