Returns image Mime type

getImageMimeType.php

<?php

/**
 * @param string $imageUrl
 * @return string|bool
 */
public function getImageMimeType($imageUrl) {
    $mimeTypes = [
        IMAGETYPE_GIF => "image/gif",
        IMAGETYPE_JPEG => "image/jpg",
        IMAGETYPE_PNG => "image/png",
        IMAGETYPE_ICO => "image/ico",
        IMAGETYPE_SWF => "image/swf",
        IMAGETYPE_PSD => "image/psd",
        IMAGETYPE_BMP => "image/bmp",
        IMAGETYPE_TIFF_II => "image/tiff",
        IMAGETYPE_TIFF_MM => "image/tiff",
        IMAGETYPE_JPC => "image/jpc",
        IMAGETYPE_JP2 => "image/jp2",
        IMAGETYPE_JPX => "image/jpx",
        IMAGETYPE_JB2 => "image/jb2",
        IMAGETYPE_SWC => "image/swc",
        IMAGETYPE_IFF => "image/iff",
        IMAGETYPE_WBMP => "image/wbmp",
        IMAGETYPE_XBM => "image/xbm"
    ];

    if (($imageType = exif_imagetype($imageUrl)) && (array_key_exists($imageType, $mimeTypes))) {
        return $mimeTypes[$imageType];
    } 

    return false;
}