Basic symbols and usage in PHP

Annotations:

// single line comments
Multi-line comment

Use of quotation marks

"Single quotation marks, no meaning whatsoever, take it without any processing;
"" double quotes, PHP dynamically handles and then outputs, typically used for variables.

Variable form:

One is True;
The other is False

Common variable morphology:

String (number, Chinese character, etc.)
Integer (1, 2, 3, 4, 5, 0, -1, -2, etc.)
(decimal point)
Array an array
object

Gettype ($mix) and settype($mix,$typename) can be used.

Commonly used symbols

\ "double quotation marks
\ \ the backslash
\ n line
\ r
\ t jump (TAB)

Sign of operation

+ addition operation - subtraction operation
* multiplication/division
% remainder ++ add
Add up the strings

Set the operation

= substitute the value on the right into the value on the left.
+= add the right-hand side to the left-hand side
Minus PI equals minus the right-hand side to the left-hand side
*= multiply the left-hand side by the right-hand side
/= divide the left-hand side by the right-hand side
.= add the right string to the left

A member of the operation

& and
| or
^ the mutex (xor)
< < Shift to the left
> > Shift to the right
Take the complement of 1

Logical operations

< Less than > Is greater than
< = less than or equal to > Is greater than or equal to
! = is not equal to ampersand and
| | or! Don't

Other operational symbols

$variable sign
Indicator of a variable (added before the variable)
@ does not display error message (added before function)
- > Object's methods or properties
= > The element values of the array
? : ternary operator

Basic method

1.PHP converts strings to case!

The strtolower (); Convert characters to lowercase
The strtoupper (); Convert characters to uppercase

2.PHP encrypted string (case or case)

The md5 (); encryption
Sha1 (); encryption

3. About quotes

One, the single quote is the original output

Two, the double quotation mark is the content explanation carries on the output

Anti-single quotes execute a command such as' PWD '.

Four, "\" on the translation character, such as "\n" for line break!

4. The function: htmlspecialchars ()

This function converts special characters to HTML string format (&... ; ). One of the most common situations is probably the message board for customer messages.

Ampersand becomes ampersand
"(double quotation marks) to"
< (less than) into <
> (greater than) into >

This function converts only the above special characters, not all of them to the ASCII conversion specified in HTML.

5. Batch output HTML content!

Echo < < < EOT
HTML output... // comments are still output here!
EOT;

Print < < < EOT
HTML output... // comments are still output here!
EOT;

(note: "{variable}" is used to contain variables internally.)

6. Determine whether the file exists and output the contents

< ? PHP
$FileName = "File. TXT";
If (File_Exists ($FileName)) {
Echo "< Xmp>" File_Get_Contents ($FileName). "< / xmp>" ;
} the else
{
Echo "no";
}
? >

7. Uninstall variable unset;

The unset ($var);
The unset ($var, $var1);

8. Is_int;

Test whether the variable is an integer;

9. Is_null;

Detect whether the variable is NULL;

10. Is_string

Detects if the variable is a string

11. Is_real;

Is_float (alias)

12. Isset

Detects whether a variable is set

13. Is_bool

Test whether the variable is Boolean

14. Is_array

Checks whether the variable is an array

15. Is_object

Detects whether a variable is an object

16. The SubStr.

SUBSTR (String, Start, SelectNum)
Echo substr (" abcdef ", 1); / / bcdef
Echo substr (' abcdef, 1, 3); / / BCD
Echo substr (' abcdef '0, 4); / / the abcd
Echo substr (' abcdef '0, 8). / / abcdef
Echo substr (' abcdef, 1, 1); / / f

17. Nb2br

Echo nl2br (" foo isn 't \ n bar ");

Change escaped newlines to HTML < BR / >