how to get Description metadata of an image?

Question

I need to get Description metadata of an image

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

result:

FILE.FileName: img.jpg<br />
FILE.FileDateTime: 1657032928<br />
FILE.FileSize: 89183<br />
FILE.FileType: 2<br />
FILE.MimeType: image/jpeg<br />
FILE.SectionsFound: ANY_TAG, IFD0, GPS<br />
COMPUTED.html: width="576" height="680"<br />
COMPUTED.Height: 680<br />
COMPUTED.Width: 576<br />
COMPUTED.IsColor: 1<br />
COMPUTED.ByteOrderMotorola: 0<br />
IFD0.Orientation: 1<br />
IFD0.XResolution: 300/1<br />
IFD0.YResolution: 300/1<br />
IFD0.ResolutionUnit: 2<br />
IFD0.Software: GIMP 2.10.32<br />
IFD0.DateTime: 2022:07:05 16:54:23<br />
IFD0.GPS_IFD_Pointer: 148<br />
GPS.GPSAltitude: 0/100<br />

there is no Description metadata (the data is clearly visible inside GIMP, for example)

so how can I get Description metadata of an image ?

Answer 1

Different formats

(Without any link to the file you tested, I assume that...)

The reason is that Exif (Exchangeable image file format) is not the only metadata format and that it does not know any item for descriptions. Most likely, because it is primarily inserted by cameras, not programs. There are other metadata formats:

• IPTC (International Press Telecommunications Council) :
  record 2 ("application"), dataset 120 ("Caption/Abstract : A textual description of the objectdata, particularly used where the object is not text. ")
• XMP (Extensible_Metadata_Platform) :
  a description element in any namespace, mostly <dc:description>
• RIFF (Resource Interchange File Format) :
  INFO chunk, but without any "description" item
• QTFF (QuickTime File Format) :
  list atoms ©des , desc , ldes , sdes , dscp , or key atom com.apple.quicktime.description

Files versus metadata

Which meta formats can be expected in which file formats?

File formats \ Metadata formats	Exif	IPTC	XMP	RIFF	QTFF	proprietary
JFIF/JPEG	✓	✓	✓			comment
TIFF, CR2, ORF, DNG, RAW, JPEG-XR, NIFF, MDI	✓	✓	✓			many
PNG, JNG, MNG	✓	✓	✓			free text
GIF			✓			comment
WebP	✓		✓	✓		many
JPEG2000, JPEG-XL, HEIF	✓	✓	✓		✓	many
PSD	✓	✓	✓			caption

Finding description in multiple metadata formats in JFIFile

PHP can by default parse Exif and IPTC and XML (XMP's format), along with JFIFiles. Combining all this we can find a JFIF's description either in IPTC or XMP metadata, should it be there. Technically descriptions can occur more than once per metadata, and (of course) all of those can differ.

<?php
    // Don't let the browser interpret this as HTML
    header( 'Content-Type: text/plain; charset=UTF-8' );


    // Add finding to overall array and take note of metadata format in which it was found
    function found( &$aFound, $sText, $sMeta ) {
        if( !isset( $aFound[$sText] ) ) {  // Text is new?
            $aFound[$sText]= $sMeta; 
        } else {
            $aFound[$sText].= ', '. $sMeta;  // Text is known already, just add metadata format
        }
    }


    // Store all findings: key=text, value=metadata format(s)
    $aFound= array();

    // Parse picture, only JFIF/JPEG picture is supported for metadata
    getimagesize( 'C:/mypic.jpg', $aMeta );

    // Any metadata found at all?
    if( is_array( $aMeta ) )
    foreach( $aMeta as $sType=> $sData ) {
        switch( $sType ) {
            case 'APP13':  // IPTC
                $aIptc= iptcparse( $sData );
                if( is_array( $aIptc ) ) {  // Might have failed
                    if( isset( $aIptc['2#120'] ) ) {
                        // In theory tags can occur multiple times
                        foreach( $aIptc['2#120'] as $sDesc ) {
                            found( $aFound, $sDesc, 'IPTC' );
                        }
                    }
                }
            break;

            case 'APP1':  // Mostly XMP, but can also be Exif
                $iStart= strpos( $sData, '<x:xmpmeta' );
                $iEnd= strpos( $sData, '</x:xmpmeta>', $iStart+ 10 );
                if( $iStart> 0&& $iEnd> 0 ) {  // Valid XMP
                    $sData= substr( $sData, $iStart, $iEnd- $iStart+ 12 );

                    $oDom= new DOMDocument();
                    $oDom-> loadXml( $sData );  // Parse XML data
                    $oXpath= new DOMXpath( $oDom );
                    $oXpath-> registerNamespace( 'rdf', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#' );  // Resource Description Framework
                    $oXpath-> registerNamespace( 'dc', 'http://purl.org/dc/elements/1.1/' );  // Dublin Core

                    // First the document/file itself, then in its context the picture related info
                    foreach( $oXpath-> evaluate( '//rdf:Description//dc:description' ) as $oElem ) {
                        if( $oElem-> nodeValue ) found( $aFound, $oElem-> nodeValue, 'XMP' ); else
                        if( $oElem-> textContent ) found( $aFound, $oElem-> textContent, 'XMP' );
                    }
                }
            break;
        }
    }


    // Which texts have we found?
    print_r( $aFound );

Related questions/answers

• read XMP description field with php (actually reading IPTC)
• Get Value of XML/XMP tag in PHP (parsing XML of XMP instead of using regular expressions)