srv01 ~ # emerge -av php

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild  N    ] app-text/recode-3.6_p16  USE="nls" 2,021 kB
[ebuild  N    ] net-libs/c-client-2007e  USE="pam ssl -kolab" 2,725 kB
[ebuild   R   ] dev-lang/php-5.3.3-r1  USE="apache2* berkdb bzip2 calendar* cgi cjk* cli crypt ctype curl* curlwrappers* enchant* exif* fileinfo filter flatfile* ftp* gd gdbm hash iconv imap* intl* ipv6 json kerberos mysql* mysqli* nls phar posix readline recode* session sharedext* simplexml snmp soap* sockets* spell sqlite sqlite3 ssl threads tidy tokenizer truetype unicode xml xmlreader xmlwriter zip zlib -adabas -bcmath -birdstep -cdb -concurrentmodphp -db2 -dbmaker -debug -doc -embed -empress -empress-bcs -esoob -firebird -fpm -frontbase -gd-external -gmp -inifile -interbase -iodbc -kolab -ldap -ldap-sasl -libedit -mssql -mysqlnd -oci8 -oci8-instant-client -odbc -pcntl -pdo -pic -postgres -qdbm -sapdb -sharedmem -solid -suhosin -sybase-ct -sysvipc -wddx -xmlrpc -xpm -xsl" 0 kB

Total: 3 packages (2 new, 1 reinstall), Size of downloads: 4,745 kB

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

dev-lang/php:5

  ('installed', '/', 'dev-lang/php-5.3.3-r1', 'nomerge') pulled in by
    =dev-lang/php-5.3.3-r1[-imap,-mysql,-mysqli] required by ('ebuild', '/', 'dev-lang/php-5.3.3-r1', 'merge')
    (and 1 more)

  ('ebuild', '/', 'dev-lang/php-5.3.3-r1', 'merge') pulled in by
    php

  Explanation:

    New USE for 'dev-lang/php:5' are incorrectly set. In order to solve
    this, adjust USE to satisfy '=dev-
    lang/php-5.3.3-r1[-imap,-mysql,-mysqli]'.