The PHP-function each() has been deprecated as of PHP 7.2.0 (https://wiki.php.net/rfc/deprecations_php_7_2#each). It has been fixed in T174354
for the MediaWiki-Core, but the vendor-directory still contains each()-function-calls:

pear/mail_mime
vendor/pear/mail_mime/Mail/mimePart.php:

while (list($idx, $line) = each($lines)) {

vendor/pear/mail_mime/Mail/mime.php:

while (list($key, $value) = each($params)) {

vendor/pear/mail_mime/Mail/mime.php:

while (list($key, $value) = each($params)) {

pear/pear-core-minimal
vendor/pear/pear-core-minimal/src/PEAR.php:

while (list($k, $objref) = each($_PEAR_destructor_object_list)) {

pear/console_getopt
vendor/pear/console_getopt/Console/Getopt.php:

while (list($i, $arg) = each($args)) {

vendor/pear/console_getopt/Console/Getopt.php:

} else if (list(, $opt_arg) = each($args)) {

vendor/pear/console_getopt/Console/Getopt.php:

if (!strlen($opt_arg) && !(list(, $opt_arg) = each($args))) {

pear/mail_mime-decode
vendor/pear/mail_mime-decode/Mail/mimePart.php:

while(list(, $line) = each($lines)){

vendor/pear/mail_mime-decode/Mail/mimeDecode.php:

while (list($key, $value) = each($headers)) {

vendor/pear/mail_mime-decode/Mail/mimeDecode.php:

while (list($p_name, $p_value) = each($content_type['other'])) {

vendor/pear/mail_mime-decode/Mail/mimeDecode.php:

while (list($p_name, $p_value) = each($content_disposition['other'])) {

vendor/pear/mail_mime-decode/Mail/mime.php:

while (list($key, $value) = each($build_params)) {

ruflin/elastica
vendor/ruflin/elastica/lib/Elastica/Transport/Http.php:

while (list($header, $headerValue) = each($headersConfig)) {

vendor/ruflin/elastica/lib/Elastica/Multi/MultiBuilder.php:

list($key, $search) = each($searches);

phpunit/phpunit
vendor/phpunit/phpunit/src/Util/Getopt.php on line 38:

while (list($i, $arg) = each($args)) {