Can php delete constants?

PHP cannot delete constants, reasons: 1. When assigning a constant to a variable, it actually assigns a value, but it is still a constant; 2. Once a constant is defined, it cannot be replaced

#php cannot delete constants, only variables.

Assigning a constant to a variable is actually assigning a value, but it is still a constant.

All constants cannot be deleted.

And the constants you define cannot be changed, they are fixed.

Evidence: define defines a constant define(constant name, value);

Proof 1: The constant cannot be deleted

<?php
define(&#39;abc&#39;,&#39;abc&#39;);
unset(abc);
?>

Execution result: Syntax Error

Parse error: syntax error, unexpected ')', expecting T_PAAMAYIM_NEKUDOTAYIM in C:\wamp\www\Untitled-1.php on line 11

Certificate 2: Once a constant is defined, it cannot be replaced

<?php
define(&#39;abc&#39;,&#39;abc&#39;);
echo abc;
define(&#39;abc&#39;,&#39;bcd&#39;);
echo abc;
?>

Result: (Error message: Note that abc is already a constant.)

abc
Notice: Constant abc already defined in C:\wamp\www\Untitled-1.php on line 12
abc

<?php
$abc=false;
echo $abc.&#39;<br>&#39;;//空白
$abc=&#39;我是变量&#39;;
ecoh $abc;
?>

Use directly $ defines all variables.

Relevant learning recommendations: php graphic tutorial

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