这里显示系统所支持的所有函数,和自定义函数
Array
(
    [internal] => Array
        (
            [0] => zend_version
            [1] => func_num_args
            [2] => func_get_arg
            [3] => func_get_args
            [4] => strlen
            [5] => strcmp
            [6] => strncmp
            [7] => strcasecmp
            [8] => strncasecmp
            [9] => each
            [10] => error_reporting
            [11] => define
            [12] => defined
            [13] => get_class
            [14] => get_called_class
            [15] => get_parent_class
            [16] => method_exists
            [17] => property_exists
            [18] => class_exists
            [19] => interface_exists
            [20] => trait_exists
            [21] => function_exists
            [22] => class_alias
            [23] => get_included_files
            [24] => get_required_files
            [25] => is_subclass_of
            [26] => is_a
            [27] => get_class_vars
            [28] => get_object_vars
            [29] => get_class_methods
            [30] => trigger_error
            [31] => user_error
            [32] => set_error_handler
            [33] => restore_error_handler
            [34] => set_exception_handler
            [35] => restore_exception_handler
            [36] => get_declared_classes
            [37] => get_declared_traits
            [38] => get_declared_interfaces
            [39] => get_defined_functions
            [40] => get_defined_vars
            [41] => create_function
            [42] => get_resource_type
            [43] => get_resources
            [44] => get_loaded_extensions
            [45] => extension_loaded
            [46] => get_extension_funcs
            [47] => get_defined_constants
            [48] => debug_backtrace
            [49] => debug_print_backtrace
            [50] => gc_mem_caches
            [51] => gc_collect_cycles
            [52] => gc_enabled
            [53] => gc_enable
            [54] => gc_disable
            [55] => strtotime
            [56] => date
            [57] => idate
            [58] => gmdate
            [59] => mktime
            [60] => gmmktime
            [61] => checkdate
            [62] => strftime
            [63] => gmstrftime
            [64] => time
            [65] => localtime
            [66] => getdate
            [67] => date_create
            [68] => date_create_immutable
            [69] => date_create_from_format
            [70] => date_create_immutable_from_format
            [71] => date_parse
            [72] => date_parse_from_format
            [73] => date_get_last_errors
            [74] => date_format
            [75] => date_modify
            [76] => date_add
            [77] => date_sub
            [78] => date_timezone_get
            [79] => date_timezone_set
            [80] => date_offset_get
            [81] => date_diff
            [82] => date_time_set
            [83] => date_date_set
            [84] => date_isodate_set
            [85] => date_timestamp_set
            [86] => date_timestamp_get
            [87] => timezone_open
            [88] => timezone_name_get
            [89] => timezone_name_from_abbr
            [90] => timezone_offset_get
            [91] => timezone_transitions_get
            [92] => timezone_location_get
            [93] => timezone_identifiers_list
            [94] => timezone_abbreviations_list
            [95] => timezone_version_get
            [96] => date_interval_create_from_date_string
            [97] => date_interval_format
            [98] => date_default_timezone_set
            [99] => date_default_timezone_get
            [100] => date_sunrise
            [101] => date_sunset
            [102] => date_sun_info
            [103] => libxml_set_streams_context
            [104] => libxml_use_internal_errors
            [105] => libxml_get_last_error
            [106] => libxml_clear_errors
            [107] => libxml_get_errors
            [108] => libxml_disable_entity_loader
            [109] => libxml_set_external_entity_loader
            [110] => openssl_get_cert_locations
            [111] => openssl_spki_new
            [112] => openssl_spki_verify
            [113] => openssl_spki_export
            [114] => openssl_spki_export_challenge
            [115] => openssl_pkey_free
            [116] => openssl_pkey_new
            [117] => openssl_pkey_export
            [118] => openssl_pkey_export_to_file
            [119] => openssl_pkey_get_private
            [120] => openssl_pkey_get_public
            [121] => openssl_pkey_get_details
            [122] => openssl_free_key
            [123] => openssl_get_privatekey
            [124] => openssl_get_publickey
            [125] => openssl_x509_read
            [126] => openssl_x509_free
            [127] => openssl_x509_parse
            [128] => openssl_x509_checkpurpose
            [129] => openssl_x509_check_private_key
            [130] => openssl_x509_export
            [131] => openssl_x509_fingerprint
            [132] => openssl_x509_export_to_file
            [133] => openssl_pkcs12_export
            [134] => openssl_pkcs12_export_to_file
            [135] => openssl_pkcs12_read
            [136] => openssl_csr_new
            [137] => openssl_csr_export
            [138] => openssl_csr_export_to_file
            [139] => openssl_csr_sign
            [140] => openssl_csr_get_subject
            [141] => openssl_csr_get_public_key
            [142] => openssl_digest
            [143] => openssl_encrypt
            [144] => openssl_decrypt
            [145] => openssl_cipher_iv_length
            [146] => openssl_sign
            [147] => openssl_verify
            [148] => openssl_seal
            [149] => openssl_open
            [150] => openssl_pbkdf2
            [151] => openssl_pkcs7_verify
            [152] => openssl_pkcs7_decrypt
            [153] => openssl_pkcs7_sign
            [154] => openssl_pkcs7_encrypt
            [155] => openssl_pkcs7_read
            [156] => openssl_private_encrypt
            [157] => openssl_private_decrypt
            [158] => openssl_public_encrypt
            [159] => openssl_public_decrypt
            [160] => openssl_get_md_methods
            [161] => openssl_get_cipher_methods
            [162] => openssl_get_curve_names
            [163] => openssl_dh_compute_key
            [164] => openssl_random_pseudo_bytes
            [165] => openssl_error_string
            [166] => preg_match
            [167] => preg_match_all
            [168] => preg_replace
            [169] => preg_replace_callback
            [170] => preg_replace_callback_array
            [171] => preg_filter
            [172] => preg_split
            [173] => preg_quote
            [174] => preg_grep
            [175] => preg_last_error
            [176] => readgzfile
            [177] => gzrewind
            [178] => gzclose
            [179] => gzeof
            [180] => gzgetc
            [181] => gzgets
            [182] => gzgetss
            [183] => gzread
            [184] => gzopen
            [185] => gzpassthru
            [186] => gzseek
            [187] => gztell
            [188] => gzwrite
            [189] => gzputs
            [190] => gzfile
            [191] => gzcompress
            [192] => gzuncompress
            [193] => gzdeflate
            [194] => gzinflate
            [195] => gzencode
            [196] => gzdecode
            [197] => zlib_encode
            [198] => zlib_decode
            [199] => zlib_get_coding_type
            [200] => deflate_init
            [201] => deflate_add
            [202] => inflate_init
            [203] => inflate_add
            [204] => inflate_get_status
            [205] => inflate_get_read_len
            [206] => ob_gzhandler
            [207] => bcadd
            [208] => bcsub
            [209] => bcmul
            [210] => bcdiv
            [211] => bcmod
            [212] => bcpow
            [213] => bcsqrt
            [214] => bcscale
            [215] => bccomp
            [216] => bcpowmod
            [217] => ctype_alnum
            [218] => ctype_alpha
            [219] => ctype_cntrl
            [220] => ctype_digit
            [221] => ctype_lower
            [222] => ctype_graph
            [223] => ctype_print
            [224] => ctype_punct
            [225] => ctype_space
            [226] => ctype_upper
            [227] => ctype_xdigit
            [228] => curl_init
            [229] => curl_copy_handle
            [230] => curl_version
            [231] => curl_setopt
            [232] => curl_setopt_array
            [233] => curl_exec
            [234] => curl_getinfo
            [235] => curl_error
            [236] => curl_errno
            [237] => curl_close
            [238] => curl_strerror
            [239] => curl_multi_strerror
            [240] => curl_share_strerror
            [241] => curl_reset
            [242] => curl_escape
            [243] => curl_unescape
            [244] => curl_pause
            [245] => curl_multi_init
            [246] => curl_multi_add_handle
            [247] => curl_multi_remove_handle
            [248] => curl_multi_select
            [249] => curl_multi_exec
            [250] => curl_multi_getcontent
            [251] => curl_multi_info_read
            [252] => curl_multi_close
            [253] => curl_multi_errno
            [254] => curl_multi_setopt
            [255] => curl_share_init
            [256] => curl_share_close
            [257] => curl_share_setopt
            [258] => curl_share_errno
            [259] => curl_file_create
            [260] => dom_import_simplexml