PHP Common special operation symbols and function summary (PHP beginners must SEE) _php skills

Callout symbol:
single-line annotation
Multi-line annotation
Use of Quotes
' single quotes, simple strings, without any processing directly brought over;
"" Double quotes, PHP dynamic processing and then output, generally used to process the $ variable.
Boolean variable:
One is true;
The other one is false or false.
Common variables:
string strings (digital \ Kanji \ etc.)
Integer integers (1, 2, 3, 4, 5, 0,-1,-2, etc.)
Double floating-point number (decimal point)
Array arrays
Object objects
The methods available are GetType ($mix) and Settype ($mix, $typename);

Common symbol Escape:

\ "Double Quotes
\ reverse Slash
\ n Line Change
\ r back to the beginning
\ t Horizontal Tabulation
operator Symbol:
+ addition operation-subtraction operation
* Multiplication Operations/Division operations
% to take remainder + + since add 1
--from minus 1. Connect two strings
Assignment Operation:
= Put the right value into the left
+ = Add the right value to the left
-= reduce the value on the right to the left
*= multiply the value on the left to the right.
/= divide the value on the left to the right.
. = Add the right string to the left
bit operations:
& Bitwise AND
| by bit or
^ Bitwise exclusive OR (XOR)
<< move 1-bit to the left
>> Move 1 digits to the right
~ Take the complement number
Logical Operations:
< less than > greater than
<= is less than or equal to >= greater than or equal
!= not equal to && and
||      Or! Non -
Other operational symbols
$ variable Symbol
& Variable Alias
@ Do not display error message (added to function)
Methods or properties of the-> object
The element value of the => array
?: Ternary operator

Common basic methods:

1.PHP conversion string is case-insensitive!

Strtolower (); Turn characters to lowercase
Strtoupper (); Capitalize the character

2.PHP Encrypted string

Not to be restored:
MD5 ();
SHA1 ();
To restore:
Base64_encode ();
Base64_decode ();

3. About Quotes

One, single quotation mark is the original output
Two, double quotes are content interpretation for output
The reverse single quotation mark (Keng number) is executed with a system command such as ' dir '. Commonly used in table names, field names above.
Four, "\" for the translation of characters, such as "\ n" for line wrapping.

4. Functions: Htmlspecialchars () and Htmlentities ()
This function converts special characters into an HTML string format (&....;). The most commonly used occasions may be to deal with the message version of the customer message.

& (and) Convert to &
"(double quotes) into"
< (less than) turn into <
> (greater than) convert to >
(space) turn into

5. Bulk Output HTML content!

Echo <<< EOT
HTML Output content ... Here the annotation still output!
EOT;

Print <<<eot
HTML Output content ... Here the annotation still output!
EOT;
(Note: Internal contains variables with "{variable}")

6. Determine if the file exists and output content file_exists ()

<?php
$FileName = "File.TXT";
if (file_exists ($FileName)) {
echo "<pre>". file_get_contents ($FileName). " </pre> ";
}else
{
echo "No";
}
?>

7. Delete variable release memory unset ();

Unset ($var);
Unset ($var, $var 1);

8.is_numeric;
Detect whether the variable is a number;

9.is_int;
Detects whether a variable is an integer;

10.is_null;
Detects whether the variable is NULL;

11.is_string
Detects whether a variable is a string

12.is_real;
Alias for Is_float ()

13.isset
Detect whether a variable is defined

14.is_bool
Detect whether a variable is a Boolean

15.is_array
Detects whether a variable is an array

16.is_object
Detects whether a variable is an object

The 17.SUBSTR () function returns part of the string.

SUBSTR (String,start,selectnum)

Copy Code code as follows:

echo substr (' abcdef ', 1); Bcdef
echo substr (' abcdef ', 1, 3); Bcd
echo substr (' abcdef ', 0, 4); Abcd
echo substr (' abcdef ', 0, 8); ABCdef
echo substr (' abcdef ',-1, 1); F

18.NB2BR () turns the escaped newline into an HTML <br/>

Copy Code code as follows:

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