PHP Learning Notes

Directory 1.PHP variable 2.PHP constant 3.PHP string 4.PHP array 5.PHP function

I. PHP base 1.PHP variables

Header("content-type:text/html; Charset=utf-8 ");/*PHP has three different variable scopes: local (local) global (global) static (static)*///variables declared outside the function have Global scope and can only be accessed outside of the function. Variables declared inside a function have a local scope and can only be accessed inside the function.     $x= 5;//Global Scope    functionmyTest () {$y= 10;//Local Scope    } //The Global keyword is used to access variables within the function.     $x=5; $y=10; functionmyTest () {Global $x,$y; $y=$x+$y;    } myTest (); Echo $y;//The output 15//php also stores all global variables in an array named $GLOBALS [index]. The subscript contains the variable name. $GLOBALS [' x '] = 5//$GLOBALS [' y '] = ten

2.PHP Constants

Header("content-type:text/html; Charset=utf-8 ");//valid constant names begin with a character or underscore (there is no $ symbol in front of the constant name). /*to set a constant, use the Define () function-it uses three parameters: 1. The first parameter defines the name of a constant 2. The second parameter defines the value of the constant 3. The optional third parameter specifies whether the constant name is case-sensitive. The default is False. *///constants that are case sensitiveDefine("Greeting", "Welcome");Echogreeting;//constants that are not sensitive to caseDefine("Greeting", "Welcome",true);Echogreeting;

3.PHP string

//1. The difference between single and double quotes    #String variables directly contained in double quotation marks    #the contents of a single quote string are always considered ordinary characters    $str= ' Hello '; Echo"Str is$str";//Run Result: STR is Hello    Echo' Str is $str ';//operation Result: STR is $str//2. Remove whitespace from the end of a string    #trim removes spaces at both ends of a string.     #RTrim is to remove a string to the right of the space    #LTrim is to remove the left space of a string//3. Gets the length of the string    #English character length    strlen($str); #Chinese character lengthMb_strlen ($str, "UTF8");//4. Interception of Strings    #The Intercept function of the English string substr ()    #substr (string variable, start intercept position, intercept number)    $str= ' I love You '; Echo substr($str, 2, 4); #intercept function of Chinese string mb_substr ()    #mb_substr (string variable, start intercept position, intercept number, page encoding)    $str= ' I love you, China '; EchoMB_SUBSTR ($str, 4, 2, ' UTF8 ');//5. String Lookup    #Strpos (string to be processed, string to position, starting position of position [optional])    $str= ' I want to study at IMOOC '; $pos=Strpos($str, ' Imooc ');//6. String substitution    #Str_replace (The string to find, the string to replace, the string to be searched, and the replacement to count [optional])    $str= ' I want to learn JS '; $replace=Str_replace(' JS ', ' php ',$str);//7. Merging and splitting of strings    #string merge function implode (): Combining array elements into a single string    #implode (delimiter [optional], array)    $arr=Array(' Hello ', ' world! '); $result=implode(‘‘,$arr); Print_r($result);//The results show Hello world!    #string-delimited function explode (): function returns an array consisting of strings    #explode (delimiter [optional], string)    $str= ' Apple,banana '; $result=Explode(‘,‘,$str); Print_r($result);//results show Array (' Apple ', ' banana ')

4.PHP arrays

//Create an empty array$str=Array();//indexed array: The key of an array is an array of integers, and the integer order of the keys starts at 0, and so on. $fruit=Array("Apple", "banana", "pineapple");//Indexed array Assignment://1. Assign a value with the name of the array variable followed by a bracket$arr[0]= ' Apple ';//Use the-= symbol to separate keys and values, the left for the key, and the right for the value. Array(' 0 ' = ' apple ');//count ($arr) returns the array length//for iterating through the values in the indexed array for($i= 0;$i<Count($fruit);$i++){    Echo"$fruit[$i]<br> ";}//foreach iterates through the values in an indexed arrayforeach($fruit  as $k=$v){    Echo $k." ...".$v." <br> ";}//indexed Array Sorting#sort arrays in ascending orderSort($fruit)#sort the array in descending orderRsort($fruit)

//associative array: The key of an exponential group is an array of strings$fruit=Array(' apple ' = ' apple ', ' banana ' and ' banana ', ' pineapple ' and ' pineapple ');//Associative array assignment//1. Assign a value with the name of the array variable followed by a bracket$arr[' Apple ']= ' apple ';//2. Use the-= symbol to separate the keys and values, the left for the key, and the right to indicate the valueArray(' apple ' = ' apple ');//The Foreach loop accesses the values in the associative arrayforeach($fruit  as $k=$v){    Echo' <br> Fruit's English Key name: '.$k. ', the corresponding value is: '.$v;}//Associative array sorting#sort associative arrays in ascending order according to the keyKsort($fruit) #sort associative arrays in descending order according to the keyKrsort($fruit) #sort associative arrays in ascending order based on valuesAsort($fruit) #sort associative arrays in descending order based on valuesArsort($fruit)

5.PHP function

// a user-defined function declaration begins with "function".//The function name can begin with a letter or an underscore (not a number). The function name is not sensitive to capitalization.  function  functionname () {  the code being executed;}


// determine if a function exists function func () {} if (function_exists(' func ')) {    echo ' exists ';}

PHP Learning Notes