PHP for case sensitive problem processing is messy, write code may occasionally problem, so here is summed up.
but I'm not encouraging people to use these rules. We recommend that you always adhere to the "case sensitive", follow the Uniform Code specifications.
One, case sensitive
1. Variable names are case-sensitive
All variables are case-sensitive, including ordinary variables as well as $_get, $_post, $_request, $_cookie, $_session, $GLOBALS, $_server, $_files, $_env, etc.
Copy Code code as follows:
<?php
$ABC = ' ABCD ';
Echo $abc; Output ' ABCD '
Echo $aBc; No output
Echo $ABC; No output
2. Constant names are case-sensitive by default, and are usually written as uppercase
(but not found to change this default configuration item, solve)
Copy Code code as follows:
1 <?php
Define ("ABC", "Hello World");
Echo ABC; Output Hello World
ECHO ABC; Output ABC
3. PHP.ini configuration item directives are case-sensitive
such as File_uploads = 1 cannot be written file_uploads = 1
Second, case insensitive
4. Function name, method name, class name is not case-sensitive, but it is recommended to use the same name as defined
Copy Code code as follows:
<?php
Function Show () {
echo "Hello World";
}
Show (); Output Hello World recommended notation
Show (); Output Hello World
Copy Code code as follows:
<?php
Class cls{
static function func () {
echo "Hello World";
}
}
Cls::func (); Output Hello World
5. Magic constants are case-insensitive and are recommended for uppercase
include: __line__, __file__, __dir__, __function__, __class__, __method__ and __namespace__.
Copy Code code as follows:
<?php
Echo __line__; Output 2
Echo __line__; Output 3
6. NULL, TRUE, false case-insensitive
Copy Code code as follows:
<?php
$a = null;
$b = NULL;
$c = true;
$d = TRUE;
$e = false;
$f = FALSE;
Var_dump ($a = = $b); Output Boolean True
Var_dump ($c = = $d); Output Boolean True
Var_dump ($e = = $f); Output Boolean True
7. Type casts, case-insensitive, including:
* (int), (integer) – converted to integral type
* (BOOL), (Boolean) – Convert to Boolean
* (float), (double), (real)-converted to floating-point
* (String)-converted to string
* (Array)-Convert array
* (object)-Convert to Object
Copy Code code as follows:
<?php
$a = 1;
Var_dump ($a); Output int 1
$b = (STRING) $a;
Var_dump ($b); Output string ' 1 ' (length=1)
$c = (string) $a;
Var_dump ($c); Output string ' 1 ' (length=1)
