Some functions of braces in php

Braces are the most common, most easily overlooked and most indispensable part of PHP. This article summarizes the three major functions of "{}" and hopes to be helpful to readers.

The three major functions of "{}" are:

Combine multiple independent statements into a compound statement, such as if ... else ... is often used like this in

to delimit variable indirect references to avoid ambiguity. For example, the difference between ${$my_var[8]} and ${$my_var}[8]

is used to indicate a single character in a string variable (the subscript starts from 0).

For example: "my_string" = "joker";

It seems that it is OK without adding it. What does adding {} mean?

Also Why should field names be included with ``?

At least it is easier to read~~~'' is required by the insert into statement, because strings must appear in pairs

Add {} Sometimes it is to prevent the variable name from being connected with the following string.

For example,

{$cid}dd

If cid=aa

then {$cid}dd=aadd

If you don’t add it, take a look at $ciddd yourself. Wouldn’t it become a ciddd variable~~

 //   The   following   is   okay   as   it's   inside   a   string.     Constants   are   not        
  //   looked   for   within   strings   so   no   E_NOTICE   error   here        
  print   "Hello   $arr[fruit]";             //   Hello   apple        
  //   With   one   exception,   braces   surrounding   arrays   within   strings        
  //   allows   constants   to   be   looked   for        
  print   "Hello   {$arr[fruit]}";         //   Hello   carrot        
  print   "Hello   {$arr['fruit']}";     //   Hello   apple

Add a brace after the PHP variable { }, filled with numbers, refers to the characters of the corresponding serial number of the PHP variable.

For example:

$str = 'hello';

echo $str{0}; // The output is h

echo $str{1 }; // The output is e

If you want to check whether a string meets the specified length, you can consider using braces (braces) plus isset to replace the strlen function, because isset is a language structure, strlen is a function, so using isset is more efficient than using strlen.

For example, to determine whether the length of a string is less than 5:

if (!isset ($str{5})) is better than if (strlen ($str) < 5).

The following explanations are more illustrative:

means that {} is a variable, and it will be processed as a variable during execution

Reference variables in strings The special inclusion method is used so that the . operator can not be used, thereby reducing the amount of code input. In fact, the output block is equivalent to print "hello ".$arr['fruit'];

The function of curly brackets in php is as follows:

1. No matter what program, function name(){}, for(){},... there are too many, and I don’t even know what they are used for.

2. $str{4} is followed by {} after the string variable. Just like the curly brackets and square brackets, a certain string variable is treated as an array.

3. {$val}, the role of the curly brackets at this time is to tell PHP that the enclosed items should be treated as variables.

$arr=array(0=>123,'name'=>'小猪');
 foreach($array as $k=>$v){
 echo "select * from blog_blogs where blog_tags like '%{$arr[$k]}%'order by blog_id"; //加一个大括号只是将作   为变量的标志符
 }
 echo '






';
 foreach($array as $k=>$v){
 echo "select * from blog_blogs where blog_tags like'%{{$arr[$k]}}%' order by blog_id"; //加两个大括号，外面的 将作为普通的字符
 }
 //用大括号来区分变量
 //echo "$arr['name']";//用此句会报语法错误
 echo "{$arr['name']}";//此句正常，大括号内的字符将作为变量来处理
 //$str{4}在字符串的变量的后面跟上{}大括号和中括号一样都是把某个字符串变量当成数组处理
 $str = 'abcdefg';
 echo $str{4};

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