通过curl检查远程URL是否是图像

Via curl from url i getting some info and i need to check if it is an image.

$result = curl_exec($ch);

UPDATE: Content-type checking is not a good idea, because it can be faked.

I would personally use gd tools within PHP to check if its an image or not. You cannot trust that the source gives the right MIME within the header. More than once I have trusted the headers and been disappionted by the fact that the content was an image but was transferred (due to the way the url/server works) over another format.

I guess one way would be to read the HTTP-headers, especially the Content-type header, and evaluate whether it is an image or not.

This SO question discuss how to check http headers using curl.

Use this to get the MIME type.

echo curl_getinfo($ch, CURLINFO_CONTENT_TYPE);

and use it against common image mime types viz. image/gif, image/png, etc.

1. Include the HTTP header in the output by setting CURLOPT_HEADER via curl_setopt.
2. Parse the header, e.g using http_parse_headers.
3. Check whether the content-type header field indicates an image type.

You might also want to set the request method to HEAD by setting CURLOPT_NOBODY if you are only interested in the content type.

function getContentType($url)
{
    $curl = curl_init();
    curl_setopt_array( $curl, array(
    CURLOPT_HEADER => true,
    CURLOPT_NOBODY => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_FOLLOWLOCATION => true,
    CURLOPT_URL => $url ) );

    curl_exec( $curl ); //execute
    $contentType = curl_getinfo($curl, CURLINFO_CONTENT_TYPE);  //get content type
    curl_close( $curl );

    return $contentType;
}

The above function will return you the type and then u can check for substring image in value returned

    $c = curl_init();

    curl_setopt( $c, CURLOPT_RETURNTRANSFER, true );
    curl_setopt( $c, CURLOPT_CUSTOMREQUEST, 'HEAD' );
    curl_setopt( $c, CURLOPT_HEADER, 1 );
    curl_setopt( $c, CURLOPT_NOBODY, true );
    curl_setopt( $c, CURLOPT_URL, 'your.url' );

    curl_exec($c);

    $content_type = curl_getinfo($c, CURLINFO_CONTENT_TYPE);

And check for allowed content-type.

You can use getimagesize

<?php
    $i = getimagesize('http://static.adzerk.net/Advertisers/bd294ce7ff4c43b6aad4aa4169fb819b.jpg');
    print_r($i);

Output

Array
(
    [0] => 220
    [1] => 250
    [2] => 2
    [3] => width="220" height="250"
    [bits] => 8
    [channels] => 3
    [mime] => image/jpeg
)

In case its not image you'll get false

$i = getimagesize('http://stackoverflow.com');
var_dump($i);

Output:

bool(false)