Composer Fails to Install Drush
APC Enabled Server
If your server is running APC, that may interfere with Composer. You'll likely see errors like this
PHP Fatal error: include(): Cannot redeclare class symfony\component\process\process in phar:///usr/local/bin/composer/vendor/composer/ClassLoader.php on line 412
You can around this problem by calling composer by way of the php cli with the argument apc.enable_cli=0.
php -d "apc.enable_cli=0" /usr/local/bin/composer global require drush/drush:7.*
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