PHP case: function and class names are not distinguished variable names are distinguished
- 2020-06-12 08:46:26
- OfStack
PHP's handling of case-sensitive issues is messy, and there may be occasional problems when writing code, so here is a summary of 1.
But I'm not encouraging you to use these rules. It is recommended that you always adhere to "case sensitive" and follow the code specification of Unified 1.
1. Variable names are case sensitive
<?php
$abc = 'abcd';
echo $abc; // The output 'abcd'
echo $aBc; // There is no output
echo $ABC; // There is no output
2. Constant names are case-sensitive by default and are usually written in uppercase
(But can not find to change this default configuration item, solve)
<?php
define("ABC","Hello World");
echo ABC; // The output Hello World
echo abc; // The output abc
3. php. ini configuration instructions are case sensitive
For example, file_uploads = 1 cannot be written as File_uploads = 1
4. Function, method, and class names are case insensitive
However, it is recommended to use the same name as defined
<?php
function show(){
echo "Hello World";
}
show (); // Output Hello World recommended
SHOW (); // Output Hello World
<?php
class cls{
static function func(){
echo "hello world";
}
}
Cls::FunC(); // The output hello world
5. Magic constants are case insensitive and upper case are recommended
Including: __LINE__, __FILE__, __DIR__, __FUNCTION__, __CLASS__, __METHOD__, __NAMESPACE__.
<?php
echo __line__; // The output 2
echo __LINE__; // The output 3
6. NULL, TRUE, FALSE are case insensitive
<?php
$a = null;
$b = NULL;
$c = true;
$d = TRUE;
$e = false;
$f = FALSE;
var_dump($a == $b); // The output boolean true
var_dump($c == $d); // The output boolean true
var_dump($e == $f); // The output boolean true
PHP variable names are case sensitive, function names are case insensitive, and small details often overlooked by newbies are tested as follows.
PHP variable name case sensitive test:
<?php
$aaa = "ofstack.com";
$AAA = "JB51.CN";
echo $aaa.'-'.$AAA; //ofstack.com-JB51.CN
?>
PHP function name is case-insensitive:
<?php
function bbb(){
echo 'abc';
}
function BBB(){
echo "Abc";
}
?>
This code will report an error :(! Fatal error: Cannot redeclare BBB()