strlen: Get the string length, byte length
substr_count The number of times a certain string appears
substr: character String interception, obtain the string (interception according to bytes)
mb_strlen
mb_substr
strchr: similar to substr, intercept from the specified position to the end
strrchr (Get file suffix name): Same as strchr, just search for characters starting from the right
strtolower: All characters are lowercase (for English letters)
strtoupper: All characters are uppercase
strrev: String reversal (only English can be reversed: English storage only has one byte), reverse by byte
strpos: Find the position where the corresponding character appears in the string ( Numeric subscript), start from the leftmost to find
strrpos: Same as strpos, just start from the right side of the string to find
trim: remove the characters on both sides of the function, the default is space
str_split function splits a string into an array.
chunk_split() function splits the string into a series of smaller parts
str_repeat("Shanghai",5);Repeat the string "Shanghai " 5 times
str_replace('\\', '/', dirname(DIR))); Replace
ucfirst capitalize the first letter
time: get the current time Timestamp (integer: starting from 0:00:00 on January 1, 1970, Greenwich Mean Time) Number of seconds
date: Time serialization function, converts the specified timestamp into the specified time and date Display format (arbitrary string: professional formatting regulations), if no timestamp is specified, the system defaults to the timestamp of the current time
strtotime: Convert a string in time and date format into the corresponding time Stamp (as long as it is a correct English time expression, it can be converted)
microtime: Microsecond timestamp, returns different results according to different requirements Mixed microtime (Boolean type), can return a floating point number Time, you can also return an array (timestamp and microseconds)
abs: absolute value
floor: round down floor(3.2) The result is equal to 3
ceil: round up
round: round up
rand: get a random integer within the specified range
mt_rand: get a specified Random integer in the range (more efficient)
min: PHP will treat non-numeric strings as 0, but if this is the smallest value, it will still return a string. If multiple parameters evaluate to 0 and are the minimum value, min() will return the smallest string in alphabetical order, or 0 of the value if there is no string;
max:PHP Non-numeric strings will be treated as 0, but if this is the largest value, a string will still be returned. If multiple arguments evaluate to 0 and are the maximum value, max() returns the numeric 0 among them, or the alphabetically largest string if there are no numeric 0s in the arguments. For multiple arrays, max is compared from left to right; if array and non-array parameters appear at the same time, the array is always returned as the maximum value;
count() // Non-array Return 1
key: Get the subscript of the element pointed to by the current pointer of the current array
current: Get the value of the element pointed to by the current pointer
next: Get the value of the next element and move the pointer down
prev: Get the value of the previous element and move the pointer up
end : Move the pointer to the last element of the array and return the value of the final pointer position
reset: Move the pointer to the last element of the array The first element, returns the value of the final pointer position
array_keys: Gets all the key names of an array and returns an index array
array_values : Get all the values of an array and return an index array
explode: Explode, divide a string into multiple arrays according to a specified rule (usually special characters) Segments, each segment is treated as an element of an array, and an index array is returned.
split is similar to explode. explode('.', 'abc.txt') is equal to split('\.', 'abc.txt')
implode: Glue, splice all the elements inside an array into a string according to a specified rule (special characters)
join() combines array elements into a string
array_merge: Merging refers to accumulating elements in two arrays. If the subsequent array has the same subscript (key name: association) as the previous array, then the value of the subsequent element will overwrite the previous one; if it is the same subscript of the index, the subscript will be automatically modified and superimposed on the previous array. inside.
array_reverse — Returns the reversed array
array_flip — Swaps the keys and values in the array
array_shift: Pop the element from the front of the array and get the value of the element
array_pop: Pop elements from the back of the array to get the value of the element
array_unshift: Push elements from the front of the array to get the number of current array elements
array_push: Push elements from the back of the array to get the number of current array elements
is_bool: Determine whether it is a Boolean type
is_float: Determine the floating point type
is_integer: Determine the integer type
is_object：Judge object
is_array：Judge array
is_string：Judge string
is_resource: Determine the resource
is_scalar: scalar is scalar, and the judgment is the basic data type: integer, floating point, Boolean And string type
is_null detects whether the variable is NULL and returns TRUE otherwise returns false. 1. Being assigned a value of NULL; 2. The variable has not been assigned a value; 3. Being unset()
is_numeric: Determine a string composed of numbers or pure numbers
gettype : Get the data type
settype: Change the data type
isset
unset() if in the function unset() is a global variable, only the local variable is destroyed, and the variables in the calling environment will keep the same value before calling unset(). If unset() is passed in the function Quoting the variable passed , only the local variable is destroyed, and the variable in the calling environment will maintain the same value before calling unset().
empty//array(),"",0,"0",NULL,FALSE all return true
opendir(path): Open a path resource (read all data inside the path into memory)
readdir(Path resource): Read the name of the file pointed to by the current resource pointer from the folder resource, and the pointer will move downward by one Bit
closedir(resource): Release the corresponding file resource
scandir(path ): Read all the file names inside a path and return an array. Each element of the array is a file name.
file_exists: Determine whether a file exists (file is a broad sense: path and file)
is_dir: Determine whether a specified path exists (file folder)
is_file: Determine whether a specified path is a file (file)
mkdir: Create a path, and an error will be reported if the path exists
rmdir：Remove the folder
file_get_contents: Read the data content from a specified file.
file_put_contents: Write the specified string to the corresponding file
fopen: Open a file resource
fgetc : c represents character, read one character at a time
fgets： s stands for string, which means multiple characters can be read, depending on the specified read length or whether a newline is encountered (up to Get a row of data)
Both functions operate on the current resource pointer. After reading, the pointer will be moved down.
fread: Get the data of the specified length until End of file
fwrite: Write data to the location where the file resource pointer is located. Writing will not move the existing things back at the current location, but will overwrite
fseek: Specify the pointer to the corresponding location
fclose: Use the corresponding file resource
copy: copy
unlink:delete file
rename:rename file
filemtime:m represents modify, the time when the file was last modified
filesize: file size (words Section)
fileperms: File permissions (octal under Linux)
rsort() function is used to sort array cells from high to low.
asort() function is used to sort the array cells from low to high and maintain the index relationship.
arsort() function is used to sort the array cells from high to low and maintain the index relationship.
ksort() function is used to sort array cells from low to high by key name.
krsort() function is used to sort array cells from high to low by key name.
error_reporting(E_ALL)
ini_set('display_errors', 1)
define() Define constant
defined() Check whether the constant is defined
serialize
unserialize
json_encode JSON encode the variable
json_decode Encoding a string in JSON format
base64_encode This function encodes the string in MIME BASE64. The string encoded by BASE64 only contains uppercase and lowercase English letters, Arabic numerals, plus signs and backslashes, a total of 64 basic characters, and does not contain other special characters, so it is named BASE64.
base64_decode decoding
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