<?php
if (exif_imagetype('imagen_subida.gif') != IMAGETYPE_GIF) {
    echo 'Hey! la imagen no es GIF!!! estas usando el tuto de sh4van3';
}else{ 
///codigo normal
}
?>

<?php
echo "test1.jpg:<br />\n";
$exif = exif_read_data('tests/test1.jpg', 'IFD0');
echo $exif===false ? "No header data found.<br />\n" : "Image contains headers<br />\n";

$exif = exif_read_data('tests/test2.jpg', 0, true);
echo "test2.jpg:<br />\n";
foreach ($exif as $key => $section) {
    foreach ($section as $name => $val) {
        echo "$key.$name: $val<br />\n";
    }
}
?>

<?php
if (array_key_exists('file', $_REQUEST)) {
    $image = exif_thumbnail($_REQUEST['file'], $width, $height, $type);
} else {
    $image = false;
}
if ($image!==false) {
    header('Content-type: ' .image_type_to_mime_type($type));
    echo $image;
    exit;
} else {
    // no thumbnail available, handle the error here
    echo 'No thumbnail available';
}
?>

function resizeImage($image,$width,$height,$scale) {
	$image_data = getimagesize($image);
	$imageType = image_type_to_mime_type($image_data[2]);
	$newImageWidth = ceil($width * $scale);
	$newImageHeight = ceil($height * $scale);
	$newImage = imagecreatetruecolor($newImageWidth,$newImageHeight);
	switch($imageType) {
		case "image/gif":
			$source=imagecreatefromgif($image); 
			break;
	    case "image/pjpeg":
		case "image/jpeg":
		case "image/jpg":
			$source=imagecreatefromjpeg($image); 
			break;
	    case "image/png":
		case "image/x-png":
			$source=imagecreatefrompng($image); 
			break;
  	}
	imagecopyresampled($newImage,$source,0,0,0,0,$newImageWidth,$newImageHeight,$width,$height);
	
	switch($imageType) {
		case "image/gif":
	  		imagegif($newImage,$image); 
			break;
      	case "image/pjpeg":
		case "image/jpeg":
		case "image/jpg":
	  		imagejpeg($newImage,$image,90); 
			break;
		case "image/png":
		case "image/x-png":
			imagepng($newImage,$image);  
			break;
    }
	
	chmod($image, 0777);
	return $image;
}
function resizeThumbnailImage($thumb_image_name, $image, $width, $height, $start_width, $start_height, $scale){
	list($imagewidth, $imageheight, $imageType) = getimagesize($image);
	$imageType = image_type_to_mime_type($imageType);
	
	$newImageWidth = ceil($width * $scale);
	$newImageHeight = ceil($height * $scale);
	$newImage = imagecreatetruecolor($newImageWidth,$newImageHeight);
	switch($imageType) {
		case "image/gif":
			$source=imagecreatefromgif($image); 
			break;
	    case "image/pjpeg":
		case "image/jpeg":
		case "image/jpg":
			$source=imagecreatefromjpeg($image); 
			break;
	    case "image/png":
		case "image/x-png":
			$source=imagecreatefrompng($image); 
			break;
  	}
	imagecopyresampled($newImage,$source,0,0,$start_width,$start_height,$newImageWidth,$newImageHeight,$width,$height);
	switch($imageType) {
		case "image/gif":
	  		imagegif($newImage,$thumb_image_name); 
			break;
      	case "image/pjpeg":
		case "image/jpeg":
		case "image/jpg":
	  		imagejpeg($newImage,$thumb_image_name,90); 
			break;
		case "image/png":
		case "image/x-png":
			imagepng($newImage,$thumb_image_name);  
			break;
    }
	chmod($thumb_image_name, 0777);
	return $thumb_image_name;
}
	chmod($thumb_image_name, 0755);
	return $thumb_image_name;
}

function getHeight($image) {
	$size = getimagesize($image);
	$height = $size[1];
	return $height;
}

function getWidth($image) {
	$size = getimagesize($image);
	$width = $size[0];
	return $width;
}


$large_image_location = $upload_path.$large_image_name;
$thumb_image_location = $upload_path.$thumb_image_name;


if(!is_dir($upload_dir)){
	mkdir($upload_dir, 0755);
	chmod($upload_dir, 0755);
}

<?php 

include'ARCHIVO-CON-EL-CODIGO-ANTERIOR.php'; 

if ($_POST["upload"]=="Upload") { 
	//RECIBE DATOS
	$userfile_name = $_FILES['image']['name'];
	$userfile_tmp = $_FILES['image']['tmp_name'];
	$userfile_size = $_FILES['image']['size'];
	$userfile_type = $_FILES['image']['type'];
	$filename = basename($_FILES['image']['name']);
	$file_ext = strtolower(substr($filename, strrpos($filename, '.') + 1));
	

	if((!empty($_FILES["image"])) && ($_FILES['image']['error'] == 0)) {
		
		foreach ($allowed_image_types as $mime_type => $ext) {

			if($file_ext==$ext && $userfile_type==$mime_type){
				$error = "";
				break;
			}else{
				$error = "Only <strong>".$image_ext."</strong> images accepted for upload<br />";
			}
		}
		//VERIFICA EL TAMAÑO
		if ($userfile_size > ($max_file*1048576)) {
			$error.= "Images must be under ".$max_file."MB in size";
		}
		
	}else{
		$error= "Please select an image for upload";
	}
	//SI TODO ESTA BIEN SUBE LA IMAGEN
	if (strlen($error)==0){
		
		if (isset($_FILES['image']['name'])){
/*/VERIFICA LA EXTENSION QUE ES TOMADA POR UNA SESION ESTA PARTE DE LA APLICACION NO HA SIDO PUBLICADA EN ESTE EJEMPLO ESTE ES MERO EJEMPLO DE EMPLEO DE LAS FUNCIONES CITADAS EN ESTE PAPER*/
			$large_image_location = $large_image_location.".".$file_ext;
			$thumb_image_location = $thumb_image_location.".".$file_ext;
			
			//UNA VEZ CARGADO EL ARCHIVO SE AGREGA LA EXTENSION TOMANDO DESDE SESION 
			if($_SESSION['user_file_ext']!=$file_ext){
				$_SESSION['user_file_ext']="";
				$_SESSION['user_file_ext']=".".$file_ext;
			}
			
			move_uploaded_file($userfile_tmp, $large_image_location);
			chmod($large_image_location, 0777);
			
			$width = getWidth($large_image_location);
			$height = getHeight($large_image_location);
			//REDUCE LA IMAGEN SI ES MAYOR EN ANCHO QUE EL PERMITIDO
			if ($width > $max_width){
				$scale = $max_width/$width;
				$uploaded = resizeImage($large_image_location,$width,$height,$scale);
			}else{
				$scale = 1;
				$uploaded = resizeImage($large_image_location,$width,$height,$scale);
			} ?>