Quick fix (1)-PHP: Overview, constants, variables, operators, expressions, control statements

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Quick fix (1)-PHP: Overview, constants, variables, operators, expressions, control statements

Webabcd


Introduced
Quick and fast PHP

• Overview
• Constant
• Variable
• Operator
• An expression
• Control statements

Example
1. Overview
basic/summary.php

<!--    PHP overview --><?  PHPecho "I am between PHP start tag and end tag"; Echo "<br/>"; if (time ()% 2 = = 0):?>     I am HTML (used to demonstrate PHP and HTML    mixed)else:?>     here is HTML (used to demonstrate PHP and HTML mixed    )endif;? ><? PHP Echo "Can not have PHP end tag"; Echo "<br/>";

2. Constants
basic/constant.php

<?PHP/** * Constant*///use define to define constantsDefine("MyConst1", "MyConst1");EchoMyConst1;Echo"<br/>";//Const is supported for defining constants after PHP 5.3.0ConstMyConst2 = "MyConst2";EchoMyConst2;Echo"<br/>";/** Magic Constants (Magic constant) * Magic constants, different values in different scenarios*///__line__-The current line number in the file, determined by its row in the scriptEcho __line__;Echo"<br/>";//__file__-The full path and file name of the current file, and if used in the included file, returns the included filenameEcho __file__;Echo"<br/>";//__DIR__-The directory where the file resides, and if used in the included file, returns the directory where the included file is locatedEcho__dir__;Echo"<br/>";//__function__-function name//__CLASS__-class name//__method__-method name//__namespace__-namespace name//__trait__-TRAIT name

3. Variables
basic/variable.php

<?PHP/** * Variable*///defining variables by $$a= "a";//by using a variableEcho $a;//output:aEcho"<br/>";//by using a variable, the variable is also used even if you add double quotes outsideEcho"$a";//output:aEcho"<br/>";//Using {} to define the variable name, such as "$ab", PHP uses the variable $ab, and in fact we want to use a $ A, at this point we can define the variable name by {}, as follows:Echo"{$a}b ";//Output:abEcho"<br/>";//add double quotes outside, but you don't want to use a variable, you can change the "$" to a string by using the "\" character .Echo"\ $a";//output: $aEcho"<br/>";//If you put a single quote outside, it's treated as a string.Echo' $a ';//output: $aEcho"<br/>";//assigning values between variables$b=$a;//define references by &. The following example is for $c reference $a$c= &$a;//re-assigning a value to a $a$a= "AA";Echo"$b";//output:aEcho"<br/>";Echo"$c";//Output:aaEcho"<br/>";functionF1 () {//The $a here refers to the $a of the local variable, but there is no $a defined in the local scope of the F1, so you have to use $a it will not have any content    Echo $a;//Output:    Echo"<br/>";} F1 ();functionF2 () {//The global keyword is used to mark the $a, and after this local scope, the $a will be used when the world version $a    Global $a; Echo $a;//Output:aa    Echo"<br/>";} F2 ();functionF3 () {//use the global version of the specified variable directly by $GLOBALS    Echo $GLOBALS[' A '];//Output:aa    Echo"<br/>";} F3 ();functionf4 () {//static variables are defined through static, and their resident memory    Static $i= 0; Echo $i; Echo"<br/>"; $i++;} F4 (); //output:0F4 ();//output:1F4 ();//Output:2$x= "AAA";//variable variables (mutable variable), the value of the variable as the variable name//the following sentence is equivalent to $aaa = "BBB"; (because the value of $x is AAA, $ $x equals $aaa)$$x= "BBB";Echo $aaa;//output:bbbEcho"<br/>";Echo$$x;//output:bbbEcho"<br/>";$s= "12345";//the effect of curly braces: used to indicate a single character in a string variable (subscript starting from 0)$s{1} = ' x ';Echo $s;//output:1x345Echo"<br/>";//the role of curly braces: used to define the name of the variable (for example, the variables used below are $s, not $ss)Echo"{$s}s ";//output:1x345sEcho"<br/>";

4, operators, expressions, control statements
basic/statement.php

<?PHP/** * operator, expression, control statement*///operators, expressions, control statements, and other languages are almost//below write something that the individual thinks needs to be emphasized//. String Operators$s 1= "Hello";$s 2= "WEBABCD";$s 3=$s 1.$s 2;Echo $s 3;//Output:hello WEBABCDEcho"<br/>";$s 1. = "Wanglei";//Output:hello WangleiEcho $s 1;Echo"<br/>";//the difference between = = and = = =$a 1= "1";//string$b 1= 1;//Integral type$c 1= "1";//stringif($a 1==$b 1)//two different types of data do = = comparison, the system will automatically convert{    Echo' $a 1 = = $b 1 ';//output: $a 1 = = $b 1    Echo"<br/>";}if($a 1===$b 1)//two different types of data do = = = comparison, the system does not automatically convert{    //not established}if($a 1===$c 1){    Echo' $a 1 = = = $c 1 ';//output: $a 1 = = = $c 1    Echo"<br/>";}//The ElseIf and else if are the same for If/else statements with the {} mode or the {} method omittedif(1 = = 2)    Echo"1 = = 2";Else if(1 = = 1)    Echo"1 = = 1";ElseIf(2 = = 2)    Echo"2 = = 2";Else    Echo"Else";Echo"<br/>";//for: The If/else statement of the way, only ElseIf can be used instead of the else ifif(1 = = 2):Echo"1 = = 2";//else if (1 = = 1)://echo "1 = = 1";ElseIf(2 = = 2):Echo"2 = = 2";Else:Echo"Else";endif;Echo"<br/>";//usage of the foreach statement$array 1=Array(1, 2, 3, 4);foreach($array 1  as $value){    Echo $value; Echo"<br/>";}foreach($array 1  as $key=$value){    Echo $key. " - " .$value; Echo"<br/>";}//use of Try Catch finallyTry{    Echo"Try"; Echo"<br/>"; Throw New Exception("error message", 999);//If you want to write a custom Exception, then inherit Exception .}Catch(Exception $ex){    Echo"Catch"; Echo"<br/>"; Echo sprintf("Message:%s, code:%d, File:%s, line:%d, trace:%s",$ex->getmessage (),$ex->getcode (),$ex->getfile (),$ex->getline (),$ex-gettraceasstring ()); Echo"<br/>";} finally{Echo"Finally"; Echo"<br/>";}

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Quick fix (1)-PHP: Overview, constants, variables, operators, expressions, control statements