How to check if an image exists in a remote URL?

Question

In order to have the administration of a website to be performed from a server other than the one where the website is hosted, the problem of dealing with remote images has arisen.

Common problems:

• Check if the image actually exists before linking to it;
• When replacing a particular image, check if the previous one exists to be deleted;
• Check that the image uploaded to the server is not named after an existing image.

Normally, this type of operations is carried out with the is_file(), but as it does not support URL, only absolute or relative paths of the server itself, it is thus impossible for this scenario.

Question

Using PHP, how can I check if a remote image exists?

Answer 1

For this you use the file_exists, apart from remote URL it works with absolute or relative paths of the server itself, in this way:

    if(file_exists('http://www.dominio.com/imagens/minha-imagem.jpg')){
       //seu código...
    }

other useful functions are:

• is_readable - It says if the file can be read.
• file - Reads the entire file to an array
• file_get_contents - Reads the entire file to a string (extremely useful)
• fread - Binary-safe file reading
• readfile - Reads and displays the contents of a file

Answer 2

My approach to dealing with this issue is to use Client URL Library (Curl) ^(English) to collect the HTTP Status code ^(English) and with the same knowing whether or not the image exists in the given URL:

/**
 * URL Exists
 *
 * Verifica se o caminho URL existe.
 * Isso é útil para verificar se um arquivo de imagem num 
 * servidor remoto antes de definir um link para o mesmo.
 *
 * @param string $url           O URL a verificar.
 *
 * @return boolean
 */
function url_exists($url) {

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_NOBODY, true);
    curl_exec($ch);
    $code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);

    return ($code == 200); // verifica se recebe "status OK"
}

Example of use:

$url = 'http://www.example.com/minha_imagem.jpg';
if (url_exists($url))
    // encontrei :)
else
    // não encontrei :(

---

^{Note: This solution depends on functions added from PHP 4.0.2.}

Answer 3

I’ve set up the function below that can check both images and web pages, or any other content that comes from the web. I get the answer from header request and compare codes. If 200 or 302 exists; if so 500 has internal error on the server; if 404 there is no.

It is worth remembering that who will make the request is your web server, and the same should have access to internet.

<?php
function validarext($url)
{
    $validar = get_headers($url);
    $validar = explode(" ",$validar[0]);
    $validar = $validar[1];
    if($validar == "302" || $validar == "200")
        return true;
    else
        return false;
}

if(validarext("http://www.urldaimagem.com.br/imagem.jpg")){
    //Imagem existe
    echo "Sim";
}
else
{
    //Imagem não existe...
    echo "Não";
}
?>

Answer 4

In the system that implements fileUpload you do a routine that will search if a certain photo already exists. This function will be useful for all processes:

1º: As said, check if the photo exists before creating the links to it, how to do it is using the implementation of file_exists();. It is recommended that you use a database to store the name of your file so you can request it and check with the absolute path of your server.

2º: When verified that the image exists, and soon was informed the execution of the substitution process, you will delete the existing image using the unlink() function; and soon after recover the new image of ~temp and rename it to the name that is in the database.

3º: Implement a hash pattern to add to your files, every time someone uploads a file, take the file name and concatenate with the following statement uniquid( Rand(6, 8) );

<?php

$nome = $_FILE['image']['name'];
$novoNome = $nome . uniquid( rand(6, 8) );