04PHP base-constant definition output 04PHP base-array definition and use

The definition constants of constants are case-sensitive by default, if define (' AA ', 20,true) denotes case-insensitive, the output name is generally capitalizedBOOL  Define (  string $name  ,  Mixed $value  [,  BOOL $case_insensitive = False ]) ? The constant name must be caused by ' or ' because he is a string type Constants must be declared and judged using the "" ' output when the constant name can be used directlyThe value of a constant cannot be modified, and a permanent use is defined once1.define (' AA ', +);Echo AA;2.const aa= ' Chinese '; php5.3.0 after the new additionecho AA II, 1, isset () Check if the variable exists

 
   
  

  
    
   
$i=‘你好‘;
  
    
   
if(isset($i)){
  
    
   
echo ‘定义了变量‘;
  
    
   
}else{
  
    
   
echo ‘没有定义变量‘;
  
    
   
}
 
   
  

    2, defined () check if constant exists
!defined (' AA ') && exit (' Termination of program ');

 
   
  
 
    
   
define (' AA ');   
 
    
   
if (Defined (' AA ')) {  
 
    
   
< Span class= "PLN" >echo ' defines constants ';  
 
    
   
}else {  
 
    
   
< Span class= "PLN" >echo ' no constants defined ';  
 
    
   
}  /code> 
    
    
   
  
 

         3,empty () if $i is undefined or $i=0, or null ' empty string   is true, otherwise false

 
   
  
 
    
   
 $i =1;   
 
    
   
if (Empty ($i)) {  
 
    
   
< Span class= "PLN" >echo ' $i is empty ';  
 
    
   
}else {  
 
    
   
< Span class= "PLN" >echo ' $i not empty ';  
                              
    
   
} The result is $i not empty   
 
   
  
 
 

Third, exit ();   Exit           Exit (' program stops executing '); Indicates that the program terminates execution since then. Four, Magic constants
Use of single and double quotes

  
 

   
  

  
$age=20;
   
  

  
$str1=‘php-$age‘;//纯字符串
   
  

  
//echo gettype($str1);
   
  

  
echo $str1;
   
  

  
$str2="pdsjf-$age";//输出值，不引用变量直接输出hello就用‘‘
   
  

  
//echo gettype($str2);
   
  

  
echo $str2;
  
 

Array has subscript based on subscript output value, no subscript starting from 0 echo<pre>echo $ar 1[' sn '];//be sure to add single quotes, no errors, face questions
Echo </pre>

  
 

   
  
     
    

      
     

     
$ar1=array(‘sn‘=>‘李四‘,‘赵六‘,‘张三丰‘,200=>‘李勇‘,‘丽丽‘);
      
     

     
echo $ar1[1];
      
     

     
echo $ar1[‘sn‘];//一定要加单引号，不加错误，面试题
      
     

     
echo $ar1[201];
     
    


  
 

Indexed arrays make array indexes healthy and automatically assigned as numbers, such arrays are called indexed arrays
$arr 1= Array (10,20,30);
Associative arrays= = The association number$arr 2=[' hn ' and ' Henan ', ' bj ' = ' Beijing ', ' sh ' and ' Shanghai ']; php5.4 Support Later GetType () type of print output arrayEcho GetType ($arr 1), GetType ($arr 2);
Print out all the values in the array

  
 

   
  

  
方法一：用的多
   
  

  
foreach($arr2 as $v){ //用的多
   
  

  
echo $v.‘<br>‘;
   
  

  
}
   
  

  
方法二：
   
  

  
for($i=0;$i< count ($arr1);$i++){
   
  

  
echo $arr1[$i].‘<br>‘;
   
  

  
}
  
 

Key is the index key for the key array, which can be an integer integer or string value, which can be a value of an array of any type

 
   
  

  
    
   
foreach($arr2 as $k=>$v){ 
  
    
   
echo $k.‘==‘.$v.‘<br>‘;
  
    
   
}
 
   
  

PRINT_R the structure of the print output array
Print_r ($ar 1);
The most commonly used array traversal output mode, the Foreach Loop statement

  
 

   
  

  
foreach($ar1 as $k=>$v){
   
  

  
//echo $v.‘<br>‘; //输出值
   
  

  
echo $k.‘==>‘.$v.‘<br>‘;
   
  

  
//echo $k.‘<br>‘; // 输出下标 $v=>$k 可以换位置
   
  

  
}
  
 

Is_array ($r); is the array echo is_array ($r) judged? ' is an array ': ' is not an array '; In_array (' A ', $r); Do you judge if A is in the "Echo In_array (' A ', $r)? ' A is in the array ': ' A is not in the array ';Range ()Divide the interval quickly to generate an array of 1 intervals, which can be 2,3,4 ... $arr =range (' A ', ' Z ', 1);p Rint_r ($arr);explode ()Splitting a string into an array by symbol (,) is not recommended for $str= ' a,b,v,d '; $arr =explode (', ', $str);p Rint_r ($arr);implode ()The array is combined into a string $str=array (1,5,6,3) according to the split symbol, $arr =implode ('-', $str); Echo $arr; Get the click path from where to interview questionsecho $_server[' Http_referer '];
[Http_referer] = Http://localhost/aa.htmlselect count (*) from the log where rel like '%baidu% '; Echo ' <pre> ';p rint_ R ($_server); Read the clicked connection from the database which website did the customer come in from?$from = isset ($_server[' http_referver ')? $_server[' Http_referver ']:0;//0 means open directlyecho $from;//insert into log values ($from, Time), select COUNT (*) from log where rel. like '%baidu% ';

    [server_name] + localhost   get the domain name    [server_addr] + 127.0.0.1   get the IP address of the server    [server_port] = 80    [REMOTE_ADDR] = 127.0.0.1   Customer ID
echo $_server[' server_name ']. ' <br> '; Echo $_server[' server_addr ']. ' <br> '; Echo $_server[' server_addr ']. ' <br> '; all caps required
$a =$_server;echo $a [' remote_addr '];  It's best not to use it this way, it's easy to create variable confusion

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04PHP base-constant definition output 04PHP base-array definition and use