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What are mutable variables in PHP? How to understand mutable variables?
What are mutable variables in PHP? How to understand mutable variables?
We have learned so much about PHP, what are variable variables in PHP today? How to understand mutable variables? , I wonder if you have fully mastered it. If not, then follow this article to continue learning.
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Variable variables:
$s1 = "abe"; //这是一个变量，里面存储的是字符串"abe" $abc=10, echo S$s1; //??输出10
Understanding:
1, in php , an "S" is always followed by a variable name!
2. Here, the name of the variable output by echo (identified by the -th S) is: $sl, I"abe "
3, so what is output here is sabc, which is 10
4. This variable form in which "$" appears continuously is the so-called "variable variable"
The code is as follows:
<?php $s1 = 'abc' ; //这是一个变量，里面存储的是字符串"abc" $abc= 10; // echo $$s1; //???,输出10 ?>
The running results are as follows:
The code is as follows:
The following demonstrates the flexibility of "variable variables":
The so-called variable variables actually mean that the name of the variable can be "dynamically changed" to obtain different data values
$v1 = 1;
$v2 = 12;
$v3 = 33;
$v4 = 44;
$v5 =115;
//求这5个变量的和:
//其他语言，只能“一个一个”加起来。
$sum = 0; //用于存储总和
for($i = 1; $i <= 5; $i++){
$v ="v".$i; //这里，结果其实只是一个“字符串”，比如"v1","v2" ...
$sum += $$v;
}
echo "<br />sum = $sum";
?>Running results As follows:
Recommended learning: php video tutorial
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