จะตรวจสอบว่าที่อัพโหลดขึ้นมา เป็น ข้อมูลรูปภาพ ได้อย่างไร

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<form action="" method="post" enctype="multipart/form-data">
  <input type="file" name="xxxx" id="xxxx">
  <input type="submit" name="button" id="button" value="Submit">
 
<?
if ($_FILES['xxxx'][type]=="image/jpeg") { echo "นี่คือรูปภาพนะ"; } else { echo "นี่ไม่ไช่รูปภาพคืออะไรก็ไม่รู้"; }
?>
</form>

if($_FILES['txtconfig_logo']['name']){
	$config_logo = $_FILES['txtconfig_logo']['name'];  //image name
	$tmp_name = $_FILES['txtconfig_logo']['tmp_name']; //Temp Polily	

    $fmrandom = time();
    $blogo0 = explode(".",$config_logo);
    $blogo1=count($blogo0)-1; // split choose file name
    $blogoextension=strtolower($blogo0[$blogo1]); // make extension file
    $blogo_file_name ="blogo". $fmrandom.".".$blogoextension; // full filename
    $blogouploadfile = $uploadDir.basename($blogo_file_name);
	
   if($blogoextension !="jpg" && $blogoextension !="gif" && $blogoextension !="png"){	 //Only accept jpg,gif,png
					//Error Message Box Not file accepted
	$text="Your extension file is: $blogoextension ,We accept file extension .jpg, .gif and .png only.";
	msgbox($text,$movetourl);
	}
}