Summary of the role of braces in PHP

As a PHP programmer, I have very high requirements for code, and the symbols in the code are also very particular. We often use braces (curly brackets) when writing code, so you know when Are these braces used? In fact, it is very particular. There are basically three situations when using curly braces in PHP. The following article summarizes these three usage situations.

1.

function name(){}， for(){}

I won’t go into details about this situation, I already know what it is used for.

2. $str{4} follows the string variable followed by {} braces or square brackets [], with numbers filled in. Here, the string variable is treated as an array. An example is as follows:

 <?php    
$str=&#39;phpernote.com&#39;;    
echo $str{0}; // 输出 p    
echo $str[1]; // 输出 h    
$str=&#39;000&#39;;    
$str{0}=&#39;1&#39;;    
 echo $str; // 输出 100

Note: This feature can be used to check whether a string meets the specified length. Use isset instead of the strlen function. Because isset is a language structure and strlen is a function, use isset isset is more efficient than using strlen. For example, to determine whether the length of a string is less than 5, as follows:

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

3. Use braces for variable variables, such as: {$val}. At this time, the braces tell PHP that the enclosed part should be treated as a variable. The following example:

<?php    
 $array=array(&#39;www&#39;,&#39;name&#39;=>&#39;phpernote&#39;,&#39;com&#39;);    
echo "$array[&#39;name&#39;]";//用此句会报语法错误    
echo "{$array[&#39;name&#39;]}";//此句正常，大括号内的字符将作为变量来处理

Note: ${$a[1]} is completely different from ${$a}[1]:

${$a[1]} Here$ a[1] is a variable;

${$a}[1] Here $a is a variable;

The advantage of this way of writing is that when referencing variables in a string, This eliminates the need to use the . operator, thereby reducing the amount of code typing.

Although the above three methods are very simple, they will give you a more basic understanding of braces, so that we can more easily master the skills of using braces in our studies. .

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