Are php function names case sensitive?

PHP’s handling of case-sensitive issues is messy, and problems may occasionally occur when writing code, so this article will summarize it below. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

But I am not encouraging everyone to use these rules. It is recommended that everyone always adhere to "case sensitivity" and follow unified coding standards.

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(); //Output Hello World Recommended writing method

SHOW(); / /Output Hello World

<?php
 class cls{
 static function func(){
 echo "hello world";
 }
 }
 Cls::FunC(); //输出hello world

4. Magic constants are not case-sensitive. It is recommended to use uppercase letters

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, functions 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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