PHP – exif_imagetype() function

The EXIF (Exchangeable image file format) PHP extension enables you to work with metadata from images taken by digital devices like digital cameras and cell phones. The exif_imagetype() function determines the type of an image by reading its first bytes and checking its signature. This is useful for validating file types before processing or checking browser compatibility.

Syntax

int exif_imagetype(string $filename)

Parameters

The function accepts a single parameter:

• $filename − Path to the image file to check

Return Value

Returns an integer constant representing the image type when a valid signature is found, or false on failure.

Imagetype Constants

Example 1: Detecting JPEG Image

This example demonstrates detecting a JPEG image type ?

<?php
   // Check image type
   $filetype = exif_imagetype('images/sample.jpg');
   
   if ($filetype !== false) {
       echo "The file type is: " . $filetype;
       echo "\nImage type constant: " . ($filetype === IMAGETYPE_JPEG ? 'IMAGETYPE_JPEG' : 'Other');
   } else {
       echo "Unable to determine image type";
   }
?>

The file type is: 2
Image type constant: IMAGETYPE_JPEG

Example 2: Detecting PNG Image

This example shows detection of a PNG image type ?

<?php
   // Check PNG image type
   $filetype = exif_imagetype('images/sample.png');
   
   if ($filetype !== false) {
       echo "The file type is: " . $filetype;
       echo "\nImage type constant: " . ($filetype === IMAGETYPE_PNG ? 'IMAGETYPE_PNG' : 'Other');
   } else {
       echo "Unable to determine image type";
   }
?>

The file type is: 3
Image type constant: IMAGETYPE_PNG

Practical Usage

Common use case for validating uploaded files ?

<?php
   function validateImageType($filename) {
       $allowedTypes = [IMAGETYPE_JPEG, IMAGETYPE_PNG, IMAGETYPE_GIF];
       $imageType = exif_imagetype($filename);
       
       if ($imageType === false) {
           return false;
       }
       
       return in_array($imageType, $allowedTypes);
   }
   
   // Usage
   if (validateImageType('upload.jpg')) {
       echo "Valid image file";
   } else {
       echo "Invalid image file";
   }
?>

Conclusion

The exif_imagetype() function provides a reliable way to detect image file types by examining file signatures rather than relying on file extensions. It's essential for validating uploads and ensuring compatibility with image processing functions.