The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.
Descriptions and uses for these constants are described within the curl_setopt(), curl_multi_setopt() and curl_getinfo() documentation.
CURLOPT_AUTOREFERER
    (integer)
   CURLOPT_DNS_USE_GLOBAL_CACHE
    (integer)
   CURLOPT_DNS_CACHE_TIMEOUT
    (integer)
   CURLOPT_FTP_SSL
       (integer)
     CURLFTPSSL_TRY
       (integer)
     CURLFTPSSL_ALL
       (integer)
     CURLFTPSSL_CONTROL
       (integer)
     CURLFTPSSL_NONE
       (integer)
     CURLOPT_PRIVATE
       (integer)
     CURLOPT_FTPSSLAUTH
       (integer)
     CURLOPT_PORT
    (integer)
   CURLOPT_FILE
    (integer)
   CURLOPT_INFILE
    (integer)
   CURLOPT_INFILESIZE
    (integer)
   CURLOPT_URL
    (integer)
   CURLOPT_PROXY
    (integer)
   CURLOPT_VERBOSE
    (integer)
   CURLOPT_HEADER
    (integer)
   CURLOPT_HTTPHEADER
    (integer)
   CURLOPT_NOPROGRESS
    (integer)
   CURLOPT_NOBODY
    (integer)
   CURLOPT_FAILONERROR
    (integer)
   CURLOPT_UPLOAD
    (integer)
   CURLOPT_POST
    (integer)
   CURLOPT_FTPLISTONLY
    (integer)
   CURLOPT_FTPAPPEND
    (integer)
   CURLOPT_FTP_CREATE_MISSING_DIRS
    (integer)
   CURLOPT_NETRC
    (integer)
   CURLOPT_FOLLOWLOCATION
    (integer)
   CURLOPT_FTPASCII
    (integer)
   CURLOPT_PUT
    (integer)
   CURLOPT_MUTE
    (integer)
   CURLOPT_USERPWD
    (integer)
   CURLOPT_PROXYUSERPWD
    (integer)
   CURLOPT_RANGE
    (integer)
   CURLOPT_TIMEOUT
    (integer)
   CURLOPT_TIMEOUT_MS
    (integer)
   CURLOPT_TCP_NODELAY
    (integer)
   CURLOPT_POSTFIELDS
    (integer)
   CURLOPT_PROGRESSFUNCTION
    (integer)
   CURLOPT_REFERER
    (integer)
   CURLOPT_USERAGENT
    (integer)
   CURLOPT_FTPPORT
    (integer)
   CURLOPT_FTP_USE_EPSV
    (integer)
   CURLOPT_LOW_SPEED_LIMIT
    (integer)
   CURLOPT_LOW_SPEED_TIME
    (integer)
   CURLOPT_RESUME_FROM
    (integer)
   CURLOPT_SSLCERT
    (integer)
   CURLOPT_SSLCERTPASSWD
    (integer)
   CURLOPT_WRITEHEADER
    (integer)
   CURLOPT_SSL_VERIFYHOST
    (integer)
   CURLOPT_SSLVERSION
    (integer)
   CURL_SSLVERSION_DEFAULT
    (integer)
   CURL_SSLVERSION_TLSv1
    (integer)
   CURL_SSLVERSION_SSLv2
    (integer)
   CURL_SSLVERSION_SSLv3
    (integer)
   CURL_SSLVERSION_TLSv1_0
    (integer)
   CURL_SSLVERSION_TLSv1_1
    (integer)
   CURL_SSLVERSION_TLSv1_2
    (integer)
   CURLOPT_TIMECONDITION
    (integer)
   CURLOPT_TIMEVALUE
    (integer)
   CURLOPT_CUSTOMREQUEST
    (integer)
   CURLOPT_STDERR
    (integer)
   CURLOPT_TRANSFERTEXT
    (integer)
   CURLOPT_RETURNTRANSFER
    (integer)
   CURLOPT_QUOTE
    (integer)
   CURLOPT_POSTQUOTE
    (integer)
   CURLOPT_INTERFACE
    (integer)
   CURLOPT_KRB4LEVEL
    (integer)
   CURLOPT_HTTPPROXYTUNNEL
    (integer)
   CURLOPT_FILETIME
    (integer)
   CURLOPT_WRITEFUNCTION
    (integer)
   CURLOPT_READFUNCTION
    (integer)
   CURLOPT_PASSWDFUNCTION
    (integer)
   CURLOPT_HEADERFUNCTION
    (integer)
   CURLOPT_MAXREDIRS
    (integer)
   CURLOPT_MAXCONNECTS
    (integer)
   CURLOPT_CLOSEPOLICY
    (integer)
   CURLOPT_FRESH_CONNECT
    (integer)
   CURLOPT_FORBID_REUSE
    (integer)
   CURLOPT_RANDOM_FILE
    (integer)
   CURLOPT_EGDSOCKET
    (integer)
   CURLOPT_CONNECTTIMEOUT
    (integer)
   CURLOPT_CONNECTTIMEOUT_MS
    (integer)
   CURLOPT_SSL_VERIFYPEER
    (integer)
   CURLOPT_CAINFO
    (integer)
   CURLOPT_CAPATH
    (integer)
   CURLOPT_SSL_CIPHER_LIST
    (integer)
   CURLOPT_BINARYTRANSFER
    (integer)
   CURLOPT_NOSIGNAL
    (integer)
   CURLOPT_PROXYTYPE
    (integer)
   CURLOPT_BUFFERSIZE
    (integer)
   CURLOPT_HTTPGET
    (integer)
   CURLOPT_HTTP_VERSION
    (integer)
   CURLOPT_SSLKEY
    (integer)
   CURLOPT_SSLKEYTYPE
    (integer)
   CURLOPT_SSLKEYPASSWD
    (integer)
   CURLOPT_SSLENGINE
    (integer)
   CURLOPT_SSLENGINE_DEFAULT
    (integer)
   CURLOPT_SSLCERTTYPE
    (integer)
   CURLOPT_CRLF
    (integer)
   CURLOPT_ENCODING
    (integer)
   CURLOPT_PROXYPORT
    (integer)
   CURLOPT_UNRESTRICTED_AUTH
    (integer)
   CURLOPT_FTP_USE_EPRT
    (integer)
   CURLOPT_HTTP200ALIASES
    (integer)
   CURLOPT_HTTPAUTH
    (integer)
   CURLAUTH_BASIC
    (integer)
   CURLAUTH_DIGEST
    (integer)
   CURLAUTH_GSSNEGOTIATE
    (integer)
   CURLAUTH_NTLM
    (integer)
   CURLAUTH_ANY
    (integer)
   CURLAUTH_ANYSAFE
    (integer)
   CURLOPT_PROXYAUTH
    (integer)
   CURLOPT_MAX_RECV_SPEED_LARGE
    (integer)
   CURLOPT_MAX_SEND_SPEED_LARGE
    (integer)
   CURLCLOSEPOLICY_LEAST_RECENTLY_USED
    (integer)
   CURLCLOSEPOLICY_LEAST_TRAFFIC
    (integer)
   CURLCLOSEPOLICY_SLOWEST
    (integer)
   CURLCLOSEPOLICY_CALLBACK
    (integer)
   CURLCLOSEPOLICY_OLDEST
    (integer)
   CURLINFO_PRIVATE
    (integer)
   CURLINFO_EFFECTIVE_URL
    (integer)
   CURLINFO_HTTP_CODE
    (integer)
   CURLINFO_HEADER_OUT
    (integer)
   CURLINFO_HEADER_SIZE
    (integer)
   CURLINFO_REQUEST_SIZE
    (integer)
   CURLINFO_TOTAL_TIME
    (integer)
   CURLINFO_NAMELOOKUP_TIME
    (integer)
   CURLINFO_CONNECT_TIME
    (integer)
   CURLINFO_PRETRANSFER_TIME
    (integer)
   CURLINFO_SIZE_UPLOAD
    (integer)
   CURLINFO_SIZE_DOWNLOAD
    (integer)
   CURLINFO_SPEED_DOWNLOAD
    (integer)
   CURLINFO_SPEED_UPLOAD
    (integer)
   CURLINFO_FILETIME
    (integer)
   CURLINFO_SSL_VERIFYRESULT
    (integer)
   CURLINFO_CONTENT_LENGTH_DOWNLOAD
    (integer)
   CURLINFO_CONTENT_LENGTH_UPLOAD
    (integer)
   CURLINFO_STARTTRANSFER_TIME
    (integer)
   CURLINFO_CONTENT_TYPE
    (integer)
   CURLINFO_REDIRECT_TIME
    (integer)
   CURLINFO_REDIRECT_COUNT
    (integer)
   CURLINFO_REDIRECT_URL
    (string)
   CURLINFO_PRIMARY_IP
    (string)
   CURLINFO_PRIMARY_PORT
    (integer)
   CURLINFO_LOCAL_IP
    (string)
   CURLINFO_LOCAL_PORT
    (integer)
   CURL_TIMECOND_IFMODSINCE
    (integer)
   CURL_TIMECOND_IFUNMODSINCE
    (integer)
   CURL_TIMECOND_LASTMOD
    (integer)
   CURL_VERSION_IPV6
    (integer)
   CURL_VERSION_KERBEROS4
    (integer)
   CURL_VERSION_SSL
    (integer)
   CURL_VERSION_LIBZ
    (integer)
   CURLVERSION_NOW
    (integer)
   CURLE_OK
    (integer)
   CURLE_UNSUPPORTED_PROTOCOL
    (integer)
   CURLE_FAILED_INIT
    (integer)
   CURLE_URL_MALFORMAT
    (integer)
   CURLE_URL_MALFORMAT_USER
    (integer)
   CURLE_COULDNT_RESOLVE_PROXY
    (integer)
   CURLE_COULDNT_RESOLVE_HOST
    (integer)
   CURLE_COULDNT_CONNECT
    (integer)
   CURLE_FTP_WEIRD_SERVER_REPLY
    (integer)
   CURLE_FTP_ACCESS_DENIED
    (integer)
   CURLE_FTP_USER_PASSWORD_INCORRECT
    (integer)
   CURLE_FTP_WEIRD_PASS_REPLY
    (integer)
   CURLE_FTP_WEIRD_USER_REPLY
    (integer)
   CURLE_FTP_WEIRD_PASV_REPLY
    (integer)
   CURLE_FTP_WEIRD_227_FORMAT
    (integer)
   CURLE_FTP_CANT_GET_HOST
    (integer)
   CURLE_FTP_CANT_RECONNECT
    (integer)
   CURLE_FTP_COULDNT_SET_BINARY
    (integer)
   CURLE_PARTIAL_FILE
    (integer)
   CURLE_FTP_COULDNT_RETR_FILE
    (integer)
   CURLE_FTP_WRITE_ERROR
    (integer)
   CURLE_FTP_QUOTE_ERROR
    (integer)
   CURLE_HTTP_NOT_FOUND
    (integer)
   CURLE_WRITE_ERROR
    (integer)
   CURLE_MALFORMAT_USER
    (integer)
   CURLE_FTP_COULDNT_STOR_FILE
    (integer)
   CURLE_READ_ERROR
    (integer)
   CURLE_OUT_OF_MEMORY
    (integer)
   CURLE_OPERATION_TIMEOUTED
    (integer)
   CURLE_FTP_COULDNT_SET_ASCII
    (integer)
   CURLE_FTP_PORT_FAILED
    (integer)
   CURLE_FTP_COULDNT_USE_REST
    (integer)
   CURLE_FTP_COULDNT_GET_SIZE
    (integer)
   CURLE_HTTP_RANGE_ERROR
    (integer)
   CURLE_HTTP_POST_ERROR
    (integer)
   CURLE_SSL_CONNECT_ERROR
    (integer)
   CURLE_FTP_BAD_DOWNLOAD_RESUME
    (integer)
   CURLE_FILE_COULDNT_READ_FILE
    (integer)
   CURLE_LDAP_CANNOT_BIND
    (integer)
   CURLE_LDAP_SEARCH_FAILED
    (integer)
   CURLE_LIBRARY_NOT_FOUND
    (integer)
   CURLE_FUNCTION_NOT_FOUND
    (integer)
   CURLE_ABORTED_BY_CALLBACK
    (integer)
   CURLE_BAD_FUNCTION_ARGUMENT
    (integer)
   CURLE_BAD_CALLING_ORDER
    (integer)
   CURLE_HTTP_PORT_FAILED
    (integer)
   CURLE_BAD_PASSWORD_ENTERED
    (integer)
   CURLE_TOO_MANY_REDIRECTS
    (integer)
   CURLE_UNKNOWN_TELNET_OPTION
    (integer)
   CURLE_TELNET_OPTION_SYNTAX
    (integer)
   CURLE_OBSOLETE
    (integer)
   CURLE_SSL_PEER_CERTIFICATE
    (integer)
   CURLE_GOT_NOTHING
    (integer)
   CURLE_SSL_ENGINE_NOTFOUND
    (integer)
   CURLE_SSL_ENGINE_SETFAILED
    (integer)
   CURLE_SEND_ERROR
    (integer)
   CURLE_RECV_ERROR
    (integer)
   CURLE_SSL_CERTPROBLEM
    (integer)
   CURLE_SSL_CIPHER
    (integer)
   CURLE_SSL_CACERT
    (integer)
   CURLE_BAD_CONTENT_ENCODING
    (integer)
   CURLE_LDAP_INVALID_URL
    (integer)
   CURLE_FILESIZE_EXCEEDED
    (integer)
   CURLE_FTP_SSL_FAILED
    (integer)
   CURLE_SSH
    (integer)
   CURLFTPAUTH_DEFAULT
    (integer)
   CURLFTPAUTH_SSL
    (integer)
   CURLFTPAUTH_TLS
    (integer)
   CURLPROXY_HTTP
    (integer)
   CURLPROXY_SOCKS4
    (integer)
   CURLPROXY_SOCKS5
    (integer)
   CURL_NETRC_OPTIONAL
    (integer)
   CURL_NETRC_IGNORED
    (integer)
   CURL_NETRC_REQUIRED
    (integer)
   CURL_HTTP_VERSION_NONE
    (integer)
   CURL_HTTP_VERSION_1_0
    (integer)
   CURL_HTTP_VERSION_1_1
    (integer)
   CURLM_CALL_MULTI_PERFORM
    (integer)
   CURLM_OK
    (integer)
   CURLM_BAD_HANDLE
    (integer)
   CURLM_BAD_EASY_HANDLE
    (integer)
   CURLM_OUT_OF_MEMORY
    (integer)
   CURLM_INTERNAL_ERROR
    (integer)
   CURLMSG_DONE
    (integer)
   CURLOPT_KEYPASSWD
    (integer)
   CURLOPT_SSH_AUTH_TYPES
    (integer)
   CURLOPT_SSH_HOST_PUBLIC_KEY_MD5
    (integer)
   CURLOPT_SSH_PRIVATE_KEYFILE
    (integer)
   CURLOPT_SSH_PUBLIC_KEYFILE
    (integer)
   CURLMOPT_PIPELINING
    (integer)
   CURLMOPT_MAXCONNECTS
    (integer)
   CURLSSH_AUTH_ANY
    (integer)
   CURLSSH_AUTH_DEFAULT
    (integer)
   CURLSSH_AUTH_HOST
    (integer)
   CURLSSH_AUTH_KEYBOARD
    (integer)
   CURLSSH_AUTH_NONE
    (integer)
   CURLSSH_AUTH_PASSWORD
    (integer)
   CURLSSH_AUTH_PUBLICKEY
    (integer)
   CURL_WRAPPERS_ENABLED
    (integer)
   CURLPAUSE_ALL
    (integer)
   CURLPAUSE_CONT
    (integer)
   CURLPAUSE_RECV
    (integer)
   CURLPAUSE_RECV_CONT
    (integer)
   CURLPAUSE_SEND
    (integer)
   CURLPAUSE_SEND_CONT
    (integer)
   CURLPIPE_NOTHING
    (integer)
   CURLPIPE_HTTP1
    (integer)
   CURLPIPE_MULTIPLEX
    (integer)
   CURLPROXY_SOCKS4A
    (integer)
   CURLPROXY_SOCKS5_HOSTNAME
    (integer)