What is case insensitive in php

The following are case-insensitive in PHP: 1. Function name; 2. Method name; 3. Class name; 4. NULL; 5. TRUE; 6. FALSE; 7. Keywords; 8. Magic constants are also not case-sensitive, but uppercase is recommended.

The operating environment of this tutorial: windows10 system, PHP7.1 version, DELL G3 computer

What is not case sensitive in php

1. Variable names are case-sensitive

<?php
$abc = &#39;abcd&#39;;
echo $abc; //输出 &#39;abcd&#39;
echo $aBc; //无输出
echo $ABC; //无输出

2. Constant names are case-sensitive by default and are usually written in uppercase

<?php
define("ABC","Hello World");
echo ABC; //输出 Hello World
echo abc; //输出 abc

php.ini configuration item instructions are case-sensitive

For example, file_uploads = 1 cannot be written as File_uploads = 1

3. Function names, method names, and class names are not case-sensitive

But it is recommended to use the same name as when defined

<?php
function show(){
echo "Hello World";
}
show(); //输出 Hello World 推荐写法
SHOW(); //输出 Hello World<?php
class cls{
static function func(){
echo "hello world";
}
}
Cls::FunC(); //输出hello world

4. Magic constants are not case-sensitive, uppercase letters are recommended

Including: __LINE__, __FILE__ , __DIR__, __FUNCTION__, __CLASS__, __METHOD__, __NAMESPACE__.

<?php
echo __line__; //输出 2
echo __LINE__; //输出 3

5, NULL, TRUE, FALSE are not case-sensitive

<?php
$a = null;
$b = NULL;
$c = true;
$d = TRUE;
$e = false;
$f = FALSE;
var_dump($a == $b); //输出 boolean true
var_dump($c == $d); //输出 boolean true
var_dump($e == $f); //输出 boolean true

Summary:

In PHP, function names (custom and built-in functions), method names, class names, and keywords are not case-sensitive; but variable names are case-sensitive.

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