PHP 7.1: [] operator not supported for strings in module.audio.mp3.php

[RavanH]

While on PHPv 7.0.21 there is no problem, switching to PHPv 7.1.7 will cause the following fatal error upon a WordPress import where MP3 audio files are included.

PHP Fatal error:  Uncaught Error: [] operator not supported for strings in /var/www/wp-includes/ID3/module.audio.mp3.php:465
Stack trace:
#0 /var/www/wp-includes/ID3/module.audio.mp3.php(1088): getid3_mp3->decodeMPEGaudioHeader(916, Array, false)
#1 /var/www/wp-includes/ID3/module.audio.mp3.php(879): getid3_mp3->RecursiveFrameScanning(532, 916, true)
#2 /var/www/wp-includes/ID3/module.audio.mp3.php(1420): getid3_mp3->decodeMPEGaudioHeader(532, Array, true)
#3 /var/www/wp-includes/ID3/module.audio.mp3.php(35): getid3_mp3->getOnlyMPEGaudioInfo(166)
#4 /var/www/wp-includes/ID3/getid3.php(443): getid3_mp3->Analyze()
#5 /var/www/wp-admin/includes/media.php(3104): getID3->analyze('/var/www...')
#6 /var/www/wp-admin/includes/image.php(149): wp_read_audio_metadata('/var/www...')
#7 /var/www/wp-content/plugins/wordpress-importer/wordpress-importer.php(958): wp_generate_attachment_metadata(300, '/var/www...')
#8 /home/ in /var/www/wp-includes/ID3/module.audio.mp3.php on line 465

[SergeyBiryukov]

Hi @RavanH, thanks for the report!

We're already tracking this issue in #41496.