want to know which user was contacted from mysql database using php - php

Question

so I have a list of people with their city name and contact numbers in mysql database which is displayed on my website. I want to know which person was contacted by a visitor.
Here is a snippet of my code:
<?php
$city = $_POST['city'];
$sql = "SELECT * FROM users WHERE city = '$city'";
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
while ($row = mysqli_fetch_assoc($result)) {
$id = $row['id'];
?>
<tr>
<td class="pl-4"><?php echo "<h3>" .$row['fname']. " " .$row['lname']. "</h3>"; ?>
<BUTTON onClick="contactclick();" class="track btn btn-outline-info p-2"><span class="icon-phone"></span> Contact</BUTTON>
</td>
<script>
function contactclick() {
<?php
$sql7 = "SELECT * FROM users WHERE id = '$id' LIMIT 1";
$result7 = mysqli_query($conn, $sql7);
$row7 = mysqli_fetch_assoc($result7);
$firstname = $row7['fname'];
$lastname = $row7['lname'];
$city7 = $row7['city'];
$txt = 'Call received by:'.$firstname.' '.$lastname.' of '.$city7.'';
$file = fopen('drivers-contacted.txt','a');
fwrite($file,$txt);
?>
}
</script>
</tr>
As you can see from the code I have tried making a text file and adding info into that file everytime 'contact' button is clicked. But it adds the name of all people in the list instead of 1 who was actually contacted. How can I solve this? Also, is there a better way to get the information I want, like which user was contacted from my database list?
PS : I'm new to coding

Answer 1

In general: you are trying to communicate in the direction of client-side to server-side when you want to do a server-side action on a button click. Embedding PHP code inside the client script is not the correct way to do this. Please look up AJAX. A library called jQuery is fairly easy to use and has a simple interface for AJAX.
In addition: unless there is some code missing from this snippet, what this appears to do is create n contactclick() functions, each with its own ID. You need to take the function out of the loop, and have it accept id as a parameter. Then you can do an AJAX call from this function and your back-end (PHP) code will write to a file.