Is it necessary to memorize common functions in PHP?-PHP Problem-php.cn

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

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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