PHP Basic Syntax

Single-line Comment

/* * * Multi-line Comment

Output statement

1. Output string

print "Hello"; Only one string can be printed

echo "World"; You can print multiple strings at the same time. (a lot of use)

2. Output type (programmer test)

var_dump("AA"); You can also add variables

3. Output array

Print_r();

Weakly typed languages

You do not need to specify a type, all variables need to add $ sign

(string)$a to convert variable A to a string

settype($a, "string"); The variable A is converted to a string, and the return value is a Boolean value.

Defining strings

1. Double quotes:

$a = "Zhang San";

2. Single quotes:

$a = ' Zhang San ';

Attention:

A. The escape character can be parsed inside a double quotation mark.

$s = "Hello \" world;

Output

B. Double quotes can parse variables.

$s = "Hello {$a} world";

Output

Escape character: \ n for line break, \ r for carriage return, \ t tab, \ ", \ ', \ \

3.

$s 2=<<<A"Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >A; Var_dump ($s 2);

Output Result:

Global variables

Var_dump ($GLOBALS);

Output Result:

Variable variable

$a = "Hello"; $hello = "Zhang San"; Echo $$a;

isset($a); determine whether a $ A is defined

var_dump(isset($a)); Output result Bollinger type

unset($a); Clear variables

Empty ($a); Determine if $ A is empty

0, empty string, NULL, False

& Address

$a = ten; $b = &$a; Echo $b;

Output 10

PHP Basic Syntax