Is it necessary to memorize common functions in PHP?

Is it necessary to memorize common functions in php

No need to memorize them. There are not many commonly used functions in PHP, they are all combinations of short words. You will naturally remember it after using it for a long time. If it is really difficult to remember, you can query it through the following form.

1. PHP system functions

## serialize() Serialize $arg, that is, convert it into text to save or transmit without losing its type and structure serialize(mixed $arg) unserialize() Deserialize $str and return the type and format information before serialization unserialize($str) getcwd() Get the directory where the script is currently running getcwd() basename() Return the Chinese part of the path basename($url) preg_match() Use $string to match the regular expression, and use $res to return the matching result as matching 1 or not matching 0 preg_match($string,regular expression,$res)

Function	Function	Usage
var_dump()	Print variable structure information, including type and value. The array will recursively expand the values	var_dump($arg1...);
echo(): is a syntax structure	Outputs one or more strings , you can use single quotes or double quotes without using (). Variables are output directly,	echo$arg1,$arg2...;
isset()	Detects whether the variable is set and returns true when the value is not null, otherwise false	isset ($args)
empty()	Detect whether the variable is empty	empty($args)
exit()	Output a message and exit the current version	exit('Exit successfully')
die()	Output a message and stop the code execution	die ('Code has stopped')
iconv()	The character set is converted according to the specified encoding	iconv(incharset,outcharset,$str)
uniqid()	Get a unique ID (no parameters) or get a prefixed unique ID based on the current time microseconds (see parameters).	uniqid([prefix name], [true])
gettype()	Get the data type	gettype($ args)
settype()	Set the variable $arg to a certain data type	settype($args,"[int][string] ...")

Binary, base conversion function

##Function decbin() decoct() dechex() bindec() ##octdec() Octal ——> Decimal octdec($num) hexdec() Hexadecimal ——> Decimal hexdec($num) base_convert() Any base conversion ## The English of each base:

Function	Usage
Decimal ——> Binary	decbin($num)
Decimal ——> Octal	decoct($num)
Decimal ——> Hexadecimal	dechex($num)
Binary ——> Decimal	bindec($num)
	base_convert(the converted value,	The base of the value, the base to be converted into)

## 10 Hexadecimal: hexadecimal

3. Constant function

Function

Function

4. Judgment function

Usage define() Define constants, the third parameter selects whether it is case-sensitive. define(constant name, constant value, [true]) defined() Judge whether a constant exists define (constant name) get_defined_constants() Get predefined constants get_defined_constant() #Function Function Usage is_bool() Determine whether it is a Boolean type is_bool() is_int() Determine whether it is an integer is_int() is_string() Determine whether it is a string is_string() ##is_float() is_numeric() ##is_null() Judge whether it is empty is_null() is_array() Judge whether it is an array is_array( ) is_dir() Judge whether it is a path id_dir() 5. String function

Determine whether it is a floating point type	is_float()
Determine whether it is a number or a numeric string	is_numeric()

##Function Function returns string from $ ( $str Get the position (subscript) where $needle first appears in $str, no return false strpos($str,$needle) strrpos() Get the position (subscript) of the last occurrence of $needle in $str ), does not return false strrpos($str,$needle) substr() Intercepts the string $str from the $start position to $length strings substr($str,$start,$length) implode() Use to connect the arrays into String implode(',',$arr) explode() is used to split the string into arrays explode(',',$str) str_split() Split the string $str into an array, each unit length is 5 str_split($str,5) str_replace() Replace a with b in string $str str_replace(a ,b,$str) strtolower() Convert the string to lowercase strtolower($str) strtoupper() Convert string to uppercase strtoupper($str) ucfirst() Convert the first character of the string $str to uppercase ucfirst($str) unwords($str) trim($str) rtrim($str) strlen($str) substr_count($str,"$a") str_repeat($str,$num) strpad($str,$length,"0",STR_PAD_LEFT) strrev($str) rand(m,n) mt_rand(m,n) pow(m,n) number_format($n)

Usage		strstr() is an alias of strchr()
$str	needle The string starting from the first occurrence to the end.and is case-sensitive. If you don’t want to be case-sensitive, please use:stristr() ##strstr	,$needle)strpos()
	## unwords()	Convert the string to uppercase Convert each word in $str to capitalize the first letter
	trim()	Remove the whitespace characters at both ends of the string and Other characters
	rtrim()	Remove blank characters and other characters on the right side of the string
	strlen()	Get the string length
	substr_count()	Count the number of occurrences of a string $a in string $str
	str_repeat()	Repeat output $str, the number of times is $num
	strpad ()	Pad the left side of $str with 0 to make the length $length
	strrev()	Reverse the order of strings
	rand()	Take a random integer between m-n
	mt_rand()	Take a random integer between m-n and get the speed Faster than mt_rand()
	pow()	Take m raised to the nth power
	number_format()	Format a number with thousand separators
	6. Array function #Function Function Usage unset() unset($arr)/unset( $arr[n]) array_values() Get all the values in the array and re-establish the numeric subscript array_values($arr) array_keys() Get all key values in the array array_keys($arr) is_array() Judge whether it is an array is_array($arr) in_array() Judge whether the array $arr Contains a certain element $str in_array($str,$arr) count() Statistical array length/Statistical multi-dimensional array length count($arr)/count($arr,1) range() Create an array of 1-9 rang(1,9), range(a-z) array_merge() Connect multiple arrays into one array array_merge($ arr,$brr…) array_rand() Randomly extract n units from the array, return the key value, and become a new array array_rand($arr,n) ##shuffle() each() list(): Language structure Assign the values in the array to some variables array_unshift() array_push() array_pop() array_key_exist() array_search( ) array_flip() array_count_values() array_unique() sort() asort() maintain the index relationship rsort() arsort natsort() ksort() krsort() array_sum() key() current() next() ##prev() Move the pointer in the array forward one position prev($arr) reset() Reset the position of the pointer in the array (pointing to the one position) reset($arr) end() Move the pointer in the array to the last position end($arr) 7. Time function Destroy the specified variable Disorder the array shuffle($arr) Returns the key/value pair of the current element in the array and automatically moves the array pointer forward one step each($arr) list($a,$b,$c) =$arr Insert one or more cells at the beginning of the array array_unshift($arr,$v1,$v2. ..) Insert one or more cells at the end of the array array_push($arr,$v1,$v2… ) Remove the last element of the array and return array_pop($arr) Determine whether key $k exists in the array array_key_exist($k,$arr) Search for the given value $v in the array, and if successful, return the corresponding key name array_search($v,$arr) Exchange the keys and values of the array array_flip($arr) Statistics The number of occurrences of all values in the array array_count_values($arr) Remove duplicate values in the array array_unique($arr) Sort the array in ascending order according to the size of the value sort($arr) Arrange the array in ascending order according to the size of the value and asort($arr) Arrange the array in descending order according to the size of the value and rearrange the index rsort($arr) Arrange the array in descending order by value size, keeping the index arsort($arr) Natural sorting (in line with people’s daily usage habits) natsort($arr) Sort the array according to the key Arrange in descending order of size, retaining the association between key name and data ksort($arr) Sort the array in descending order according to the size of the key Arrange, retaining the association of key names to data krsort($arr) Sum all values in the array array_sum($arr) Get the position (key) of the traversal pointer in the array key($ arr) Get the value of the pointer position current($arr) Move the pointer in the array back one position next($arr) Function Function Usage Get the current timestamp Get the timestamp of the specified time Output the time $tmp in the specified format Parse the date and time description of any English text into a Unix timestamp ##time() time() mktime() mktime (hour, minute, second, month, Day, year) date() date('Y-m-d H:i:s',$ tmp) strtotime() strtotime("now") 8. Database functions #Function Function Function mysql_connect() Link mysql database mysql_connect($host,$user,$pwd) mysql_query() Send a MySQL statement mysql_query(sql statement) ##mysql_fetch_assoc() mysql_fetch_array() mysql_fetch_row() mysql_select_db() ##mysql_num_rows() Get the number of query result records mysql_num_rows (Query result) 9. File operation function Take out a row of data from the result set to form an associative array and return it, and continue to move the internal data pointer mysql_fetch_assoc($result) Take out a row of data from the result set to form an array and return it, and continue to move the internal data pointer mysql_fetch_array($result, parameter) Fetch a row of data from the result set to form an index array and return it, and continue to move the internal data pointer mysql_fetch_row($result) Select database mysql_select_db(database name) ##fopen() Open a file or URL ##fwrite( ) Write content in the file fwrite("filename","content") fclose() Close the file or URL fclose("filename") file_put_contents() Write content in one step file_put_contents(" filename","content") file_get_contents() Read the content in one step file_get_contents("filename","content") fread() Read the file content of the specified length fread("filename", number of bytes) filesize() Get the file content length (number of bytes) filesize("filename") fgets() Read a line fgets($handle,length) file() Read the entire file into an array file("filename") copy() Copy the file, the new file name is "newfile" copy( "filename","newfile") unlink($filename) filectime($filename) fileatime($filename) filemtime($ filename) feof($filename) json_encode($a) Decode JSON data into PHP data variables When the parameter is true, return array fopen("filename","mode") ##unlink() Delete file filectime() Get the file creation time fileatime() Get File last access time filemtime() Get file modification time feof() Determine whether the pointer reaches the end of the file json_encode（） Compile data into JSON data json_decode（） json_decode($j,[false]/true) 10. Directory operation function ##Function Function Usage mkdir() Create a directory, if there is 0777, whether to create it recursively mkdir("/path/to/my /dir", 0777); ##rmdir() Delete directory rmdir($DIR) opendir() Open directory handle opendir($dir) readdir() Read directory readdir($dir) closedir() Close the directory closedir($dir) rewinddir() Reset directory resources rewinddir($dir) file_exists() Determine whether the file/directory exists file_exists($filename/$dir) rename() Rename the file/directory rename($filename/$dir,$newname) dirname() dirname($path) Return path The directory part in basename() Returns the filename part in the path basename($path) pathinfo() Get path information pathinfo($path, [options]) 11. Class function ##Function Function Function class_exists() Determine whether the class exists class_exists($classname) interface_exists( ) Determine whether the interface exists interface_exists($name) ##method_exists() ##property_exists() Determine whether the attribute exists property($name) get_class() Get the class name get_class() get_parent_class() Get the parent Class name get_parent_class() get_class_methods() Get the methods in the class get_class_methods() get_class_vars() Returns an array consisting of the default attributes of the class get_class_vars() get_declared_class() Get the name of the defined class get_declared_class() __toString() Treat the object as a string Call __toString() __construct() Automatically call __construct() Automatically called when destroying the object Automatically called when cloning an object Automatically called when the object is called as a function Automatically called when assigning values to inaccessible member properties Automatically called when reading the value of an unreadable member attribute Automatically called when isset() or empty() is used on inaccessible member attributes Automatically call when using unset() on inaccessible member attributes Created for the class An alias Returns an association containing the defined attributes and values available for object Array Returns TRUE if the object belongs to this class or this class is the parent class of this object If the class to which object object belongs is a subclass of class class_name, return TRUE, otherwise Return FALSE. PHP Chinese website ! Determine whether the method exists method_exists($name) ## when calling New object #__destruct() __destruct() __clone() __clone() __invoke() __invoke() __set() __set() __get() __get() __isset( ) __isset() __unset() __unset() class_alias() class_alias(original class, category name) get_object_vars() get_object_vars() is_a() is_a($obj,$classname) is_subclass_of() is_subclass_of($obj,$classname) ##For more PHP related knowledge, please visit

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