Linux: How to get remote page load time with a command from the terminal?
This will give you the remote page load time in miliseconds.

time wget -p https://lateweb.info >/dev/null 2>&1
Code language: Bash (bash)

You can implement the command with php like:

<?php
$output = shell_exec('time wget -p https://lateweb.info >/dev/null 2>&1');
echo "<pre>$output</pre>";
?>
Code language: PHP (php)