PHP check file extension

For php 5.3+ you can use the SplFileInfo() class

$spl = new SplFileInfo($filename); 
print_r($spl->getExtension()); //gives extension 

Also since you are checking extension for file uploads, I highly recommend using the mime type instead..

For php 5.3+ use the finfo class

$finfo = new finfo(FILEINFO_MIME);
print_r($finfo->buffer(file_get_contents($file name)); 

$info = pathinfo($pathtofile);
if ($info["extension"] == "jpg") { .... }

pathinfo is what you're looking for

PHP.net

$file_parts = pathinfo($filename);

switch($file_parts['extension'])
{
    case "jpg":
    break;

    case "exe":
    break;

    case "": // Handle file extension for files ending in '.'
    case NULL: // Handle no file extension
    break;
}

$file_parts = pathinfo($filename);

$file_parts['extension'];
$cool_extensions = Array('jpg','png');

if (in_array($file_parts['extension'], $cool_extensions)){
    FUNCTION1
} else {
    FUNCTION2
}