remote-file-check.php

<?php
function checkRemoteFile($url)
	{
	    $ch = curl_init();
	    curl_setopt($ch, CURLOPT_URL,$url);
	    curl_setopt($ch, CURLOPT_NOBODY, 1);
	    curl_setopt($ch, CURLOPT_FAILONERROR, 1);
	    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	    if(curl_exec($ch)!==FALSE)
	    {
	        return true;
	    }
	    else
	    {
	        return false;
	    }
	}

	$url = 'https://s3.eu-west-2.amazonaws.com/test.pdf';

	$check = checkRemoteFile($url);

	if(true == $check){
		echo "ok";
	}else{
		echo "not ok";
	}
?>