PHP built-in functions (50 master)

String type

Remove left and right spaces, trim ()
The length of the string strlen ()

Float type
Array type
Count () Number of arrays

Resource Type fopen ()

Uppercase to lowercase strtolower ()
lowercase to uppercase strtoupper ()
Implode () array goto string
Explode () string to array (by custom condition)
Preg_split ('/[\s]+/', $str) string to array (by regular)
Str_split () split word array (one)

File-to-string-to-array
file_get_contents (' Abc.txt ')-string
Trim () remove left and right spaces
Preg_split ('/[\s]+/', $str) divide the array by space

Array-by-turn string (JSON)-to-file

File_put_contents ();

PHP built-in functions (50 master)