What is the difference between php functions and methods?

Difference: 1. Functions exist independently and are defined in the process-oriented part; methods depend on the class and are defined in the object-oriented part. 2. Functions can be regarded as the implementation of an algorithm; methods can be regarded as the implementation of business logic. 3. Class methods can set access permissions and need to be called through objects or classes; functions are public and can be used.

The difference between php functions and methods

1. Functions exist alone. It is defined in the process-oriented part; the method depends on the existence of the class and is defined in the object-oriented part.

2. Functions can be regarded as the implementation of an algorithm; methods can be regarded as the implementation of business logic.

3. Class methods can set access permissions and need to be called through objects or classes; functions are public and can be used.

Explanation:

The method is a "function" in the class and can only be called through the object; in particular, the static method of the class can be directly called through the class name Calling,

The function usually mentioned should be a function in the global scope, and can be called directly anywhere after being introduced.

Commonly used PHP built-in functions

排行	函数	频率	平均值
1	count	81.41 %	147.67
2	is_array	77.32 %	117.86
3	substr	74.62 %	142.92
4	in_array	74.16 %	79.55
5	explode	73.19 %	71.51
6	str_replace	72.32 %	101.05
7	implode	72.27 %	66.59
8	strlen	70.07 %	98.32
9	array_merge	69.46 %	64.01
10	strpos	67.98 %	78.18
11	preg_match	67.31 %	76.60
12	sprintf	67.16 %	119.46
13	trim	66.75 %	81.28
14	strtolower	65.99 %	59.62
15	file_exists	65.12 %	45.13
16	is_string	61.39 %	45.10
17	preg_replace	60.27 %	54.28
18	file_get_contents	59.96 %	20.71
19	array_key_exists	59.70 %	57.50
20	array_keys	59.35 %	39.59
21	dirname	56.44 %	54.84
22	function_exists	53.58 %	42.62
23	array_map	53.22 %	19.45
24	get_class	53.12 %	33.07
25	class_exists	52.50 %	23.13
26	is_object	51.94 %	35.35
27	time	51.79 %	41.42
28	json_encode	51.48 %	24.81
29	date	50.72 %	52.18
30	is_null	49.69 %	60.52
31	is_numeric	49.49 %	40.69
32	array_shift	49.49 %	23.28
33	defined	48.72 %	86.82
34	is_dir	48.57 %	22.86
35	json_decode	48.42 %	17.39
36	header	48.16 %	59.71
37	strtoupper	47.80 %	30.95
38	array_values	47.24 %	17.27
39	md5	46.88 %	23.74
40	method_exists	46.73 %	19.05
41	file_put_contents	46.68 %	12.49
42	rtrim	45.91 %	18.08
43	array_pop	45.51 %	20.60
44	unlink	44.59 %	23.55
45	basename	44.59 %	27.23
46	realpath	44.08 %	15.90
47	call_user_func	43.97 %	16.41
48	call_user_func_array	43.92 %	18.40
49	fopen	43.77 %	25.61
50	microtime	43.46 %	14.41
51	fclose	42.85 %	28.36
52	is_int	42.75 %	15.78
53	is_file	42.08 %	20.52
54	array_slice	41.83 %	13.20
55	preg_match_all	40.55 %	14.66
56	ucfirst	40.25 %	17.02
57	intval	40.19 %	88.13
58	str_repeat	40.14 %	19.51
59	serialize	40.14 %	22.05
60	array_filter	39.99 %	13.87
61	mkdir	39.79 %	11.17
62	is_callable	39.43 %	11.94
63	ltrim	39.17 %	10.90
64	ob_start	39.12 %	13.26
65	round	39.07 %	28.56
66	fwrite	38.97 %	23.39
67	array_unique	38.87 %	15.96
68	array_search	38.82 %	14.19
69	reset	38.71 %	20.79
70	array_unshift	38.10 %	10.32
71	parse_url	37.90 %	9.61
72	func_get_args	37.79 %	28.33
73	end	37.49 %	12.70
74	base64_encode	37.39 %	14.15
75	unserialize	37.18 %	18.35
76	max	36.98 %	22.88
77	preg_split	36.98 %	13.27
78	gettype	36.93 %	16.16
79	strrpos	36.67 %	11.95
80	version_compare	36.67 %	14.87
81	array_push	36.67 %	26.18
82	floor	36.11 %	18.78
83	strtotime	36.01 %	27.94
84	htmlspecialchars	35.96 %	51.08
85	ini_get	35.85 %	19.25
86	ini_set	35.60 %	14.49
87	chr	35.34 %	186.97
88	extension_loaded	35.29 %	14.17
89	is_bool	35.24 %	11.44
90	ksort	34.98 %	10.82
91	array_reverse	34.93 %	8.27
92	ord	34.73 %	53.17
93	uniqid	34.68 %	9.83
94	strtr	34.47 %	12.90
95	array_diff	34.32 %	11.13
96	error_reporting	34.17 %	8.99
97	ceil	33.35 %	11.99
98	urlencode	33.30 %	29.63
99	min	32.69 %	18.31
100	print_r	32.64 %	14.12

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