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_loaded_extensions
            [44] => extension_loaded
            [45] => get_extension_funcs
            [46] => get_defined_constants
            [47] => debug_backtrace
            [48] => debug_print_backtrace
            [49] => gc_collect_cycles
            [50] => gc_enabled
            [51] => gc_enable
            [52] => gc_disable
            [53] => strtotime
            [54] => date
            [55] => idate
            [56] => gmdate
            [57] => mktime
            [58] => gmmktime
            [59] => checkdate
            [60] => strftime
            [61] => gmstrftime
            [62] => time
            [63] => localtime
            [64] => getdate
            [65] => date_create
            [66] => date_create_from_format
            [67] => date_parse
            [68] => date_parse_from_format
            [69] => date_get_last_errors
            [70] => date_format
            [71] => date_modify
            [72] => date_add
            [73] => date_sub
            [74] => date_timezone_get
            [75] => date_timezone_set
            [76] => date_offset_get
            [77] => date_diff
            [78] => date_time_set
            [79] => date_date_set
            [80] => date_isodate_set
            [81] => date_timestamp_set
            [82] => date_timestamp_get
            [83] => timezone_open
            [84] => timezone_name_get
            [85] => timezone_name_from_abbr
            [86] => timezone_offset_get
            [87] => timezone_transitions_get
            [88] => timezone_location_get
            [89] => timezone_identifiers_list
            [90] => timezone_abbreviations_list
            [91] => timezone_version_get
            [92] => date_interval_create_from_date_string
            [93] => date_interval_format
            [94] => date_default_timezone_set
            [95] => date_default_timezone_get
            [96] => date_sunrise
            [97] => date_sunset
            [98] => date_sun_info
            [99] => ereg
            [100] => ereg_replace
            [101] => eregi
            [102] => eregi_replace
            [103] => split
            [104] => spliti
            [105] => sql