Basic symbols and usage in PHP

After using it for so long, the basic symbols of PHP were not fully recognized. I found the @ number and found it for a long time. post the basic symbol list. For more information, see ~ Annotation symbol: // single-line annotation/**/single-line annotation quotation marks are used for multiple-line annotation, which has no meaning and can be taken directly without any processing; double quotation marks, php dynamic processing and output, generally, "> <LINKhref =" http: // ww

After using it for so long, the basic symbols of PHP were not fully recognized. I found the @ number and found it for a long time. post the basic symbol list. For more information, see ~

Annotation symbol:
// Single line annotation
/**/Multi-line annotation
Use of quotation marks
''Single quotes, no meaning, can be taken without any processing;
"" Double quotes, php dynamic processing and output, usually used for variables.
Variable form:
True is True;
The other is False.
Common variables:
String (numbers, Chinese characters, etc)
Integer (1, 2, 3, 4, 5, 0,-1,-2, and so on)
Double floating point number (decimal point)
Array
Object
Available methods include gettype ($ mix) and settype ($ mix, $ typename );

Common symbols
\ "Double quotation marks
\ Backslash
\ N line feed
\ R output
\ T hop (TAB)
Operator Number
+ Addition operation-subtraction operation
* Multiplication/Division
% Get remainder + + accumulate
-- Accumulate 1. add strings
Set operation
= Place the value on the right to the left (Yes)
+ = Add the right value to the left
-= Reduce the value on the right to the left
* = Multiply the value on the left by the value on the right.
/= Divide the value on the left by the value on the right
. = Add the string on the right to the left
Bitwise operator
&
| Or
^ Exclusive (xor)
<Shift left
> Shift to the right
~ 1 Population
Logical operation
<Less> greater
<= Less than or equal to> = greater than or equal
! = Not equal to & and
| Or! No
Other operators
$ Variable symbol
& Variable indicators (before the variable)
@ Do not display the error message (before the function)
-> Object methods or attributes
=> Array element value
? : Ternary operator
Basic method
1. PHP converts strings to uppercase and lowercase!

Strtolower (); converts characters to lowercase letters
Strtoupper (); converts uppercase letters

2. PHP encrypted string (case sensitive)

Md5 (); encryption
Sha1 (); encryption

3. quotation marks

I. single quotes are output as is
2. double quotation marks are output based on content interpretation
3. a single quotation mark is used to execute a command, such as 'pwd '.
4. "\" acts on translated characters. for example, "\ n" is a line break!

4. function: htmlspecialchars ()
This function converts special characters into HTML strings (&....;). The most common use case may be the message board for handling customer messages.

& (And) &
"(Double quotation marks)"
<(Less than) to <
> (Greater than) to>

This function only converts the preceding special characters and does not convert all of them into the ASCII conversion defined in HTML.