In-depth understanding of PHP principles: variable scope (Scope in PHP)

The previous article (In-depth understanding of PHP principles: Variables inside PHP) introduced the internal representation of PHP variables, but the problem is, how do these internal representations interact with user scripts? What are the variables associated with? In other words, if I write in the script:

<?php
  $var = "laruence";
  echo $var;
?>

How does ZE connect my variable var to the internal structure zval?

As mentioned in the in-depth understanding of PHP principles and variables, PHP internally uses zval to represent variables, but for the above script, our variables have names, var. There is no corresponding field in zval to reflect the variable name.

If you think of it, there must be a mechanism inside PHP to map variable names to zval. Then you are really smart;)

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hash table to be precise), and PHP also implements variables through different arrays of the scope.

struct _zend_executor_globals {
 
     ....
    HashTable *active_symbol_table;/*活动符号表*/
    HashTable symbol_table;     /*全局符号表*/
 
    HashTable included_files;
 
    jmp_buf *bailout;
    int error_reporting;
     .....
}

Global symbol table , saves variables in the top-level scope (that is, not within any function or object). Whenever a function (method of an object) is called, an active symbol table will be created for this function, and all variables defined within this function will be saved in this active symbol table.

<?php
     $var = "I am in the global symbol table";
    function sample($para){
        $var = "I am in the active symbol table";
          echo $var;
      }
    sample($var);
    echo $var;
  ?>

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