PHP Basic Knowledge Code Summary

First, PHP base syntax variable to array

<?php//phpinfo ();       /* variable $a =1;//do not allocate space echo "\ $a =". $a;       echo "<br/>"; Var_dump ($a);//The result is a null echo "Hello Worrld"; *////* int type maximum can indicate how much echo "<br/>".       Php_int_size; echo "<br/>".       php_int_max;//(2 of 31 square-1) 31:4*8-1 sign bit $a =-2147483648;       echo "<br/>". $a;       Var_dump ($a);//The range of int is changed to float type */* Boolean $d = 0.0;           if (! $d) {echo "!!";       }*//* Floating-point number precision is 14 (starting from the left, the first non-0 is the beginning of precision) */* character single and double quotation marks $d = 90;       $d 1= "$d";       $d 2= ' $d ';       echo $d 1;       echo $d 2;*///$a =7/5.1;              echo $a;       # = = = include type also equal/* $a = 2;       $b = 2.0;           if ($a! = $b) {echo "! =";               } if ($a!== $b) #!== include type also unequal {echo "!=="; }*//* && | | As long as the previous one is true or false, then an and and or is not executed and the priority ratio = Low So $e =false or true;           The result is false, because at this point the $e is first assigned to False Var_dump ($e);          $f =true and false;//result is true, because at this point $e is first assigned true var_dump ($f); */* string concatenation $a = "1"; $b = "2";       $c = $a. $b;       */* Object type operator class dog{} $dog =new Dog;              Var_dump ($dog instanceof Dog);       $a = 3;       echo $a ++*3;//9*//* constant define ("Tax_int", 21);       # $TAX _int=9;              Echo Tax_int;       Const tax_two=0.3; echo "<br/>". Tax_two;              */* #require ' other.php ';//do not determine whether duplicate, may lead to duplicate output require_once ' other.php ';//First determine if there is a repetition of the introduction       #include ' 111other.php ';              #include_once ' other.php ';              #require and include differences: #include如果出现了错误会继续执行, #而require则会终止程序 #echo "22";       $i = 2;       $result =getnum ($i);//Pass the value, also can pass the address & echo $result; */* global variable globally $a = 1; function get () {GloBal $a;//can be used in the local $a + +;           } get ();       echo $a;       */* Array initialization//$array =array (1.2,12, "Wrwe", true);              echo count ($array);       $arr =array ("Log" = "Daomul", "Mima" =>123); echo Count ($arr). "       <br/> "; foreach ($arr as $key = + $val) {echo $key. = ". $val."           <br/> ";           } $arr 2=array ("+ =" + ",1=>" FDSF ", 23,23); echo $arr 2[""].           <br/> "; Echo $arr 2[2]. "                      <br/> ";  #使用true作为下标, that is 1, false:0;           Null: "" $arr 3=array (123.4=> "ARR3"); Echo $arr 3[123]. "                      <br/> "; #显示详细数组信息 Print_r ($arr 3);           echo "<br/>";                      Var_dump ($arr 3);           #数组可以动态增长 $arr 4=array (2,3); Echo $arr 4[1]. "        <br/> ";        $arr 4[2]= ' 11 22 333 444 ';                #echo $arr 4[2]; #字符串的拆分 Explode $arr =explode ("", $arr 4[2]);        Print_r ($arr);            foreach ($arr as $key + $val) # (array of arrays as array subscript variable to loop) {echo <br/> $key = $val ";            } echo "<br/>". $arr [1]; Unset ($arr [1]); #销毁数组元素后, the keyword subscript is not refilled with the combined Print_r ($arr); */* Array operation overlay $a =array ("a            "=>12," B "=>23);            $b =array ("A" =>21, "C" =>43);            $a = $a + $b; Print_r ($a); */?>

Second, array

Third, static variables

<?php      class child      {public          static $num =0;          public $name;          function __construct ($name)//Only new can call          {              $this->name= $name;              }              A static variable cannot access the public          function join ()          {self              :: $num +=1;  Can: Child:: $num              Echo $this->name. " You ";           }          }            $child 1=new Child ("K");      $child 1->join ();      $child 1=new Child ("a");      $child 1->join ();      $child 1=new Child ("B");      $child 1->join ();      echo "<br/>". Child:: $num;      Outside the class can only be the  class name:: Variable,          //class can be two kinds of?>
Iv. Inheritance/encapsulation/polymorphism/abstraction

/*class Child {public static $num = 0;          Public $name;              Constructor method function __construct ($name)//Only new can call {$this->name= $name;  }//Static variable cannot use this to access public function join ($ifee) {self::ifee+=1; Can: Child:: $num echo $this->name. "           You ";      }} $child 1=new child ("K");      $child 1->join ();      $child 1=new Child ("a");      $child 1->join ();      $child 1=new Child ("B");      $child 1->join (); echo "<br/>".      Child:: $num; Class can only be a class name:: Variable,//class can be two * *///Static methods can not take non-static variables, can only use non-static variables//member functions call each other, need to use $this        ->text ();        Inheritance//1, subclasses can inherit only one parent class//If you want multiple inheritance you can consider inheriting through multiple:/*class a{} class B extends a{} class C extends b{}*/ 2, the construction method in the parent class, when creating an object instance of a subclass does not default automatically call//3, the child class calls the parent class method//Parent class Name:: Method Name (); /Parent:: Method name (); Parent lowercase//overwrite: #The subclass's method and parent class have exactly the same method name and number of arguments, but do not require the same parameter name # but the modifier can be different, but the range of the child 〉= the parent class range # Parent class is private you cannot overwrite/*class a{function F () {echo ' Parent class here!        <br/> ";            }} class B extends a{} class C extends b{function F () {echo "called The parent class <br/>";            Parent::f ();        A::f ();    }} $C 1=new C (); $C 1->f (); *//abstract class: The parent class does not need to be instantiated, only the subclass inherits, can also be called inside; code reuse #抽象类 abstract class name{} #抽象方法 abstract P      Ublic cry (); #抽象类不一定也有抽象方法 #类包含抽象方法则必须为抽象类 #子类继承抽象父类, you must be an abstract class or implement all of the inherited, all!       Method//Interface: INTERFACDE interface {//attribute//Method} # can only define specification, let class to implement interface, cannot implement by itself, # Class C implements interface {}         # interfaces cannot be instantiated/interfaces can inherit other interfaces/cannot fail to implement an interface for public # A class must implement the interface and the method of its inherited interface all # (more than 1 classes of class to implement a function, but the implementation of different ways, there is no inheritance relationship,           # (2 project manager set specifications, let other programmers implement/*interface Stu {const a=90;           Public function add (); } interface stu2{} class Mystu implements Stu,stU2 {Public Function Add () {echo "dddd". Stu::a. "          <br/> ";      }} $mystu =new Mystu ();       $mystu->add (); echo "OK". stu::a;  #获得接口中的常量 *///final the methods in the class are not overwritten # Final cannot decorate member properties/*class A {final public function               Get ($salary) {return $salary;                }} class B extends A {public function get ($sal) {return $sal * *;           }} $b =new B (); $b->get ("21"); #Cannot Override final Method A::get () *///CONST constant # To assign an initial value, no subsequent assignment; f::a;  Class name:: A; Interface name:: A; The value of constant A is obtained by equal means.
V. File manipulation and error handling


<?php//File operation/* Handle the wrong way 1 if (!file_exists ("file1.txt")) {echo "Not here";  Exit ();      } else {$fp =fopen ("File1.txt", "R");      echo "File is open";  Fclose ($FP);  }*//* Handle the wrong way 2 if (!file_exists ("A.txt")) {die ("Wenjianbucunzai");  } else {} echo "end",/*//* Handle the wrong Way 1 file_exists ("B.txt") or Die ("Zhen de");  echo "End"; *///Definition Error function/*function my_error ($error, $err _message) {echo "<font size= ' 5 ' color= ' Red ' > $error &LT;/FRONT&G    T;<br/> ";//2//echo" error message is: ". $err _message;      Exit ();   }//Change the system default error handling function ("User-defined error output function", "error Type") Set_error_handler ("My_error", e_warning);       $FP =fopen ("Aa.txt", ' r '); *//Error trigger function My_error3 ($error, $err _message) {echo "Error number:". $error;           } function My_error4 ($error, $err _message) {echo "Big big!"; } set_error_handler ("My_error3", e_user_warning);//Set_error_handler ("My_error4", e_user_error);//Fatal error, do not continue execution $age =   140;    if ($age >120) {   When invoking a trigger, specify the error level Trigger_error ("the number entered is too large!")         ", E_user_error); Trigger_error ("The number entered is too large!")         ", e_user_warning);       Exit (); } echo "OK";? >
Vi. error logs

<?php  //error log php.ini in Error_log configuration  function My_error5 ($error, $err _meaasge) {       $err _info= "error message:". $ Error. " --". $err _meaasge;       echo time ();       Output current date       //     adjust time zone: The default period is UTC and China difference 8 hours PRC or asia/chongqing              date_default_timezone_set ("PRC");             echo Date ("y-m-d g-i-s");       echo "<br/>". $err _info;              #将错误存入系统文件中       Error_log ("Time is:". Date ("Y-m-d g-i-s"). " -". $err _info." \ r \ n ", 3," Myerror.txt ");//3 parameters     }     set_error_handler (" My_error5 ", e_user_warning);     $i =1;     if ($i <2)     {         Trigger_error ("the number entered is too small", e_user_warning);     }? >
Vii. Catching exceptions

<?php    //Handling exception  #注意事项: After the exception is thrown, the code will not be executed  #抛出异常之后如果没用处理则会报错  try  {      addUser ("1a");  }  catch (Exception $e)  {      echo "failure message:" $e->getmessage ();//getline ()      #可以继续抛出 throw $e;      #也可以顶一个顶级异常处理      # $i =8/0  fopen ("A.txt", "R") is difficult to throw an exception  }    function AddUser ($user)  {      if ($ user== "a")      {         echo "landed successfully! ";      }      else      {         throw new Exception ("User name is wrong!");}    }    /* #顶级异常处理  function my_error ()  {      echo "I am the top exception handler! ". E->getmeaasge ();  }  Set_error_handler ("My_error");*/?>