​What are the knowledge points you must know in PHP? (Second bullet)

We have learned so much about PHP, what are the knowledge points that you must know about PHP? Have you fully mastered it? If not, then follow this article to continue learning

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File operation function:

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 one bit

closedir (resource): Release the corresponding file resource

scandir (path): Read all 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 (folder)

is_file: Determine whether a specified path is a file (File) mkdir: Create a path. If the path exists, an error will be reported. rmdir: Remove the folder

file_get_contents: Read the data content from a specified file

Encoding:

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 decode

Serialize:

serializeunserialize

json_encode JSON encode the variable

json_decode pair The string in JSON format is encoded.

Error reporting:

error_reporting(E_ALL)

ini_set('display errors', 1)

String function:

strlen: Get the string length, byte length

substr_count the number of times a certain string appears

substr: String interception, get the string (intercept according to bytes) mb_strlen.mb_substr

strchr: Similar to substr, intercept from the specified position until the end

strrchr (get the file Suffix name): Same as strchr, just search for characters from the right strtolower: All characters are lowercase (for English letters)

strtoupper: All characters are uppercase

strrev: String reverse Reverse (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 looking from the right side of the string.

trim: Remove characters on both sides of the string. The default is spaces.

The str_split function splits the string into an array.

For a series of smaller parts

The chunk_split() function splits the string into-

str_repeat("Shanghai",5);Repeat the string "Shanghai" 5 times str_replace('l', 'T, dirname(DIR))); Replace

ucfirst capitalized

Time and date function:

time: Get the timestamp of the current time (integer: starting from 0:00:00 on January 1, 1970, Greenwich Time) number of seconds

date: time serialization function, Convert the specified timestamp into the specified time and date display format (arbitrary string: professional format specifiers are specified). If no timestamp is specified, the system defaults to the timestamp of the current time

strtotime: time Convert the date format string into the corresponding timestamp (as long as it is a correct English time expression, it can be converted)

microtime: microsecond timestamp, return different results according to different requirements. Mixed microtime ( Boolean type), can return a floating point number of time, or can return an array (timestamp and microseconds

addcslashes returns a string with a backslash added before the specified character

The htmlspecialchars function converts some predefined characters into HTML entities htmlspecialchars

decode converts some predefined HTML entities into characters

Constant:

define() defines a constant

defined() checks whether a constant is defined

Recommended study: "PHP Video Tutorial"

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