How are PHP variables defined and how does PHP work?

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1. Variable definition:

What we usually learn is that a variable represents an "identifier" for the storage space and the data in it.

The variable name points to the variable value

More deeply, the variable points to an area of memory

2. The working principle of variables, through drawing analysis method-memory space

$val){ $val = &$data[$key]; } 问：最终$data的值是多少？ */ $data = ['a','b','c']; foreach($data as $key=>$val){ $val = &$data[$key]; print_r($data); } /* 1.$key = 0, $val = 'a', $val = &$d[0] =>'a' $data = ['a','b','c']; 2.$key = 1, $val = 'b', =>$d[0] $val = &$d[1] =>'b' $data = ['b','b','c']; 1.$key = 2, $val = 'c', =>$d[1] $val = &$d[2]=>'c' $data = ['b','c','c']; */

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