print_r(get_extension_funcs('standard'));
/*
run:
Array
(
[0] => set_time_limit
[1] => header_register_callback
[2] => ob_start
[3] => ob_flush
[4] => ob_clean
[5] => ob_end_flush
[6] => ob_end_clean
[7] => ob_get_flush
[8] => ob_get_clean
[9] => ob_get_contents
[10] => ob_get_level
[11] => ob_get_length
[12] => ob_list_handlers
[13] => ob_get_status
[14] => ob_implicit_flush
[15] => output_reset_rewrite_vars
[16] => output_add_rewrite_var
[17] => stream_wrapper_register
[18] => stream_register_wrapper
[19] => stream_wrapper_unregister
[20] => stream_wrapper_restore
[21] => array_push
[22] => krsort
[23] => ksort
[24] => count
[25] => sizeof
[26] => natsort
[27] => natcasesort
[28] => asort
[29] => arsort
[30] => sort
[31] => rsort
[32] => usort
[33] => uasort
[34] => uksort
[35] => end
[36] => prev
[37] => next
[38] => reset
[39] => current
[40] => pos
[41] => key
[42] => min
[43] => max
[44] => array_walk
[45] => array_walk_recursive
[46] => in_array
[47] => array_search
[48] => extract
[49] => compact
[50] => array_fill
[51] => array_fill_keys
[52] => range
[53] => shuffle
[54] => array_pop
[55] => array_shift
[56] => array_unshift
[57] => array_splice
[58] => array_slice
[59] => array_merge
[60] => array_merge_recursive
[61] => array_replace
[62] => array_replace_recursive
[63] => array_keys
[64] => array_key_first
[65] => array_key_last
[66] => array_values
[67] => array_count_values
[68] => array_column
[69] => array_reverse
[70] => array_pad
[71] => array_flip
[72] => array_change_key_case
[73] => array_unique
[74] => array_intersect_key
[75] => array_intersect_ukey
[76] => array_intersect
[77] => array_uintersect
[78] => array_intersect_assoc
[79] => array_uintersect_assoc
[80] => array_intersect_uassoc
[81] => array_uintersect_uassoc
[82] => array_diff_key
[83] => array_diff_ukey
[84] => array_diff
[85] => array_udiff
[86] => array_diff_assoc
[87] => array_diff_uassoc
[88] => array_udiff_assoc
[89] => array_udiff_uassoc
[90] => array_multisort
[91] => array_rand
[92] => array_sum
[93] => array_product
[94] => array_reduce
[95] => array_filter
[96] => array_map
[97] => array_key_exists
[98] => key_exists
[99] => array_chunk
[100] => array_combine
[101] => array_is_list
[102] => base64_encode
[103] => base64_decode
[104] => constant
[105] => ip2long
[106] => long2ip
[107] => getenv
[108] => putenv
[109] => getopt
[110] => flush
[111] => sleep
[112] => usleep
[113] => time_nanosleep
[114] => time_sleep_until
[115] => get_current_user
[116] => get_cfg_var
[117] => error_log
[118] => error_get_last
[119] => error_clear_last
[120] => call_user_func
[121] => call_user_func_array
[122] => forward_static_call
[123] => forward_static_call_array
[124] => register_shutdown_function
[125] => highlight_file
[126] => show_source
[127] => php_strip_whitespace
[128] => highlight_string
[129] => ini_get
[130] => ini_get_all
[131] => ini_set
[132] => ini_alter
[133] => ini_restore
[134] => ini_parse_quantity
[135] => set_include_path
[136] => get_include_path
[137] => print_r
[138] => connection_aborted
[139] => connection_status
[140] => ignore_user_abort
[141] => getservbyname
[142] => getservbyport
[143] => getprotobyname
[144] => getprotobynumber
[145] => register_tick_function
[146] => unregister_tick_function
[147] => is_uploaded_file
[148] => move_uploaded_file
[149] => parse_ini_file
[150] => parse_ini_string
[151] => sys_getloadavg
[152] => get_browser
[153] => crc32
[154] => crypt
[155] => strptime
[156] => gethostname
[157] => gethostbyaddr
[158] => gethostbyname
[159] => gethostbynamel
[160] => dns_check_record
[161] => checkdnsrr
[162] => dns_get_record
[163] => dns_get_mx
[164] => getmxrr
[165] => net_get_interfaces
[166] => ftok
[167] => hrtime
[168] => md5
[169] => md5_file
[170] => getmyuid
[171] => getmygid
[172] => getmypid
[173] => getmyinode
[174] => getlastmod
[175] => sha1
[176] => sha1_file
[177] => openlog
[178] => closelog
[179] => syslog
[180] => inet_ntop
[181] => inet_pton
[182] => metaphone
[183] => header
[184] => header_remove
[185] => setrawcookie
[186] => setcookie
[187] => http_response_code
[188] => headers_sent
[189] => headers_list
[190] => htmlspecialchars
[191] => htmlspecialchars_decode
[192] => html_entity_decode
[193] => htmlentities
[194] => get_html_translation_table
[195] => assert
[196] => assert_options
[197] => bin2hex
[198] => hex2bin
[199] => strspn
[200] => strcspn
[201] => nl_langinfo
[202] => strcoll
[203] => trim
[204] => rtrim
[205] => chop
[206] => ltrim
[207] => wordwrap
[208] => explode
[209] => implode
[210] => join
[211] => strtok
[212] => strtoupper
[213] => strtolower
[214] => basename
[215] => dirname
[216] => pathinfo
[217] => stristr
[218] => strstr
[219] => strchr
[220] => strpos
[221] => stripos
[222] => strrpos
[223] => strripos
[224] => strrchr
[225] => str_contains
[226] => str_starts_with
[227] => str_ends_with
[228] => chunk_split
[229] => substr
[230] => substr_replace
[231] => quotemeta
[232] => ord
[233] => chr
[234] => ucfirst
[235] => lcfirst
[236] => ucwords
[237] => strtr
[238] => strrev
[239] => similar_text
[240] => addcslashes
[241] => addslashes
[242] => stripcslashes
[243] => stripslashes
[244] => str_replace
[245] => str_ireplace
[246] => hebrev
[247] => nl2br
[248] => strip_tags
[249] => setlocale
[250] => parse_str
[251] => str_getcsv
[252] => str_repeat
[253] => count_chars
[254] => strnatcmp
[255] => localeconv
[256] => strnatcasecmp
[257] => substr_count
[258] => str_pad
[259] => sscanf
[260] => str_rot13
[261] => str_shuffle
[262] => str_word_count
[263] => str_split
[264] => strpbrk
[265] => substr_compare
[266] => utf8_encode
[267] => utf8_decode
[268] => opendir
[269] => dir
[270] => closedir
[271] => chdir
[272] => chroot
[273] => getcwd
[274] => rewinddir
[275] => readdir
[276] => scandir
[277] => glob
[278] => exec
[279] => system
[280] => passthru
[281] => escapeshellcmd
[282] => escapeshellarg
[283] => shell_exec
[284] => proc_nice
[285] => flock
[286] => get_meta_tags
[287] => pclose
[288] => popen
[289] => readfile
[290] => rewind
[291] => rmdir
[292] => umask
[293] => fclose
[294] => feof
[295] => fgetc
[296] => fgets
[297] => fread
[298] => fopen
[299] => fscanf
[300] => fpassthru
[301] => ftruncate
[302] => fstat
[303] => fseek
[304] => ftell
[305] => fflush
[306] => fsync
[307] => fdatasync
[308] => fwrite
[309] => fputs
[310] => mkdir
[311] => rename
[312] => copy
[313] => tempnam
[314] => tmpfile
[315] => file
[316] => file_get_contents
[317] => unlink
[318] => file_put_contents
[319] => fputcsv
[320] => fgetcsv
[321] => realpath
[322] => fnmatch
[323] => sys_get_temp_dir
[324] => fileatime
[325] => filectime
[326] => filegroup
[327] => fileinode
[328] => filemtime
[329] => fileowner
[330] => fileperms
[331] => filesize
[332] => filetype
[333] => file_exists
[334] => is_writable
[335] => is_writeable
[336] => is_readable
[337] => is_executable
[338] => is_file
[339] => is_dir
[340] => is_link
[341] => stat
[342] => lstat
[343] => chown
[344] => chgrp
[345] => lchown
[346] => lchgrp
[347] => chmod
[348] => touch
[349] => clearstatcache
[350] => disk_total_space
[351] => disk_free_space
[352] => diskfreespace
[353] => realpath_cache_get
[354] => realpath_cache_size
[355] => sprintf
[356] => printf
[357] => vprintf
[358] => vsprintf
[359] => fprintf
[360] => vfprintf
[361] => fsockopen
[362] => pfsockopen
[363] => http_build_query
[364] => image_type_to_mime_type
[365] => image_type_to_extension
[366] => getimagesize
[367] => getimagesizefromstring
[368] => phpinfo
[369] => phpversion
[370] => phpcredits
[371] => php_sapi_name
[372] => php_uname
[373] => php_ini_scanned_files
[374] => php_ini_loaded_file
[375] => iptcembed
[376] => iptcparse
[377] => levenshtein
[378] => readlink
[379] => linkinfo
[380] => symlink
[381] => link
[382] => mail
[383] => abs
[384] => ceil
[385] => floor
[386] => round
[387] => sin
[388] => cos
[389] => tan
[390] => asin
[391] => acos
[392] => atan
[393] => atanh
[394] => atan2
[395] => sinh
[396] => cosh
[397] => tanh
[398] => asinh
[399] => acosh
[400] => expm1
[401] => log1p
[402] => pi
[403] => is_finite
[404] => is_nan
[405] => intdiv
[406] => is_infinite
[407] => pow
[408] => exp
[409] => log
[410] => log10
[411] => sqrt
[412] => hypot
[413] => deg2rad
[414] => rad2deg
[415] => bindec
[416] => hexdec
[417] => octdec
[418] => decbin
[419] => decoct
[420] => dechex
[421] => base_convert
[422] => number_format
[423] => fmod
[424] => fdiv
[425] => microtime
[426] => gettimeofday
[427] => getrusage
[428] => pack
[429] => unpack
[430] => password_get_info
[431] => password_hash
[432] => password_needs_rehash
[433] => password_verify
[434] => password_algos
[435] => proc_open
[436] => proc_close
[437] => proc_terminate
[438] => proc_get_status
[439] => quoted_printable_decode
[440] => quoted_printable_encode
[441] => soundex
[442] => stream_select
[443] => stream_context_create
[444] => stream_context_set_params
[445] => stream_context_get_params
[446] => stream_context_set_option
[447] => stream_context_get_options
[448] => stream_context_get_default
[449] => stream_context_set_default
[450] => stream_filter_prepend
[451] => stream_filter_append
[452] => stream_filter_remove
[453] => stream_socket_client
[454] => stream_socket_server
[455] => stream_socket_accept
[456] => stream_socket_get_name
[457] => stream_socket_recvfrom
[458] => stream_socket_sendto
[459] => stream_socket_enable_crypto
[460] => stream_socket_shutdown
[461] => stream_socket_pair
[462] => stream_copy_to_stream
[463] => stream_get_contents
[464] => stream_supports_lock
[465] => stream_set_write_buffer
[466] => set_file_buffer
[467] => stream_set_read_buffer
[468] => stream_set_blocking
[469] => socket_set_blocking
[470] => stream_get_meta_data
[471] => socket_get_status
[472] => stream_get_line
[473] => stream_resolve_include_path
[474] => stream_get_wrappers
[475] => stream_get_transports
[476] => stream_is_local
[477] => stream_isatty
[478] => stream_set_chunk_size
[479] => stream_set_timeout
[480] => socket_set_timeout
[481] => gettype
[482] => get_debug_type
[483] => settype
[484] => intval
[485] => floatval
[486] => doubleval
[487] => boolval
[488] => strval
[489] => is_null
[490] => is_resource
[491] => is_bool
[492] => is_int
[493] => is_integer
[494] => is_long
[495] => is_float
[496] => is_double
[497] => is_numeric
[498] => is_string
[499] => is_array
[500] => is_object
[501] => is_scalar
[502] => is_callable
[503] => is_iterable
[504] => is_countable
[505] => uniqid
[506] => parse_url
[507] => urlencode
[508] => urldecode
[509] => rawurlencode
[510] => rawurldecode
[511] => get_headers
[512] => stream_bucket_make_writeable
[513] => stream_bucket_prepend
[514] => stream_bucket_append
[515] => stream_bucket_new
[516] => stream_get_filters
[517] => stream_filter_register
[518] => convert_uuencode
[519] => convert_uudecode
[520] => var_dump
[521] => var_export
[522] => debug_zval_dump
[523] => serialize
[524] => unserialize
[525] => memory_get_usage
[526] => memory_get_peak_usage
[527] => memory_reset_peak_usage
[528] => version_compare
[529] => dl
[530] => cli_set_process_title
[531] => cli_get_process_title
)
*/
