Summary of common PHP functions (recommended)

1. write files 1. open the resource (file) fopen ($ filename, $ mode) 2. write file fwrite ($ handle, $ str) 3. close the file fclose ($ handle) 4. write file_put_contents ($ filename, $ str, $ mode) FILE _...

I. Writing files

1. open the resource (file) fopen ($ filename, $ mode)
2. write the file fwrite ($ handle, $ str)
3. close the file fclose ($ handle)
4. write file_put_contents ($ filename, $ str, $ mode) FILE_APPEND LOCK_EX in one step
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II. reading files
1. read the file fread ($ handle, number of bytes)
2. read a row fgets ($ handle );
3. read a character fgetc ($ handle)
4. read the file ($ filename) into an array)
5. read file_get_contents ($ filename) in one step)

III. Directory operations
1. create the directory mkdir ($ dirname)
2. delete the rmdir Directory ($ dirname)
3. open the directory handle opendir ($ dirname)
4. read the number of directory lines readdir ($ handle)
5. close the directory resource closedir ($ handle)
6. reset the directory resource rewinddir ($ dirname );

IV. Directory and file operations
1. check whether file_exists ($ filename) exists in the file or directory)
2. rename a file or directory ($ file)

V. file operations
1. copy a file ('original file', 'destination file ')
2. delete the file unlink ($ filename)
3 get the file size filesize ($ filename)
4. obtain the file creation Time: filectime ($ filename)
5. obtain the file access time fileatime ($ filename)
6. get the file modification time filemtime ($ filename)

VI. path operation 1 obtain the path dirname ($ path)
2. get the file name basename ($ path)
3. obtain the path information pathinfo ($ path)

VII. array functions (extremely important)

1. Insert an element array_unshift ($ arr, $ v) at the beginning of the array)
2. add the array element array_push ($ arr, $ v, $ v1. ..) to the end of the array ...)
3. remove the first element of the array and return the array_shift ($ arr) element)
4. delete the element array_pop ($ arr) at the end of the array)
5. connect the array with $ separator into a string implode ($ a, $ arr)
6. check whether the variable is an array is_array ($ arr)
7. obtain the array key name array_keys ($ arr)
8. obtain the array value array_values ($ arr)
9. retrieve $ value in $ arr and return the boolean value in_array ($ v, $ arr)
10. search for the key name array_key_exists ($ k, $ arr) in the array $ arr)
11. check whether $ value is in $ arr. if the return key name Array_search ($ value, $ arr) exists)
12. sort an array in reverse order. if the second parameter is true, keep the key name Array_reverse ($ arr, true)
13. swap the key and value of the array Array_flip ($ arr)
14. Count ($ arr) the number of array elements)
15. count the occurrences of all values in the array. Array_count_values ($ arr)
16. remove the repeated value Array_unique ($ arr) from the array)
17. Sort values from small to large Sort ($ arr)
18. values are sorted from large to small Rsort ($ arr)
19. Sort keys in ascending order of ksort ($ arr)
20. Sort keys in ascending order of krsort ($ arr)
21. randomly retrieve $ num elements from the array Array_rand ($ arr, $ num)
22. sum all elements of the array, Array_sum ($ arr)
23. Merge array array_merge ($ arr, $ arr)

8. string functions (extremely important)

1. output string echo ($ str) echo
2. original output (separate single quotes and double quotes) print ($ str)
3. output the string and end the script to run Die ($ str): die ($ str) die;
4. output the string and end the script to execute exit ($ str) exit;
5. output the formatted string printf ($ str, $ p1 ,...)
6. do not directly output formatted strings. return formatted strings and save them to the variables sprintf ($ str, $ p1 ,...)
7. print the variable information var_dump ($ p)
8. convert string to lower case strtolower ($ str)
9. convert string to uppercase strtoupper ($ str)
10. convert the first character of the string to uppercase ucfirst ($ str)
11. convert each word in the string to uppercase ucwords ($ str)
12. remove white spaces at both ends of the string. Trim ($ str ,',')
13. remove the white spaces on the left of the string. Ltrim ($ str)
14. remove the white spaces on the right of the string. Rtrim ($ str)
Blank characters: "", "\ t", "\ n", "\ r", "\ 0"
15 Get the string length strlen ($ str)
16 count the number of contained strings substr_count ($ str, 'substring ')
17. returns a substring starting from $ start in the string $ string with a length of $ length.
Substr ($ string, $ start [, $ length])
18. in the string $ string, $ search returns the substring that ends with the string for the first time.
Strstr ($ string, $ search)
19. search for the first position of $ search in $ str, starting from $ offset.
Strpos ($ str, $ search [, int $ offset])
20. find the last position of $ search in $ str, starting from $ offset.
Strrpos ($ str, $ search [, int $ offset])
21. replace all $ search in $ str with $ replace.
Str_replace ($ search, $ replace, $ str)
22. repeated output of the specified string
Str_repeat ()
23. encrypted string
Md5 ()
24. string flip
Strrev ()
25. use one string to separate another string to form an array // convert the string into an array
Explode ("separator", $ str );

The above is a summary of common PHP functions (recommended). For more information, see other related articles in the first PHP community!