PHP comments, variables, types, constants, operators, comparators, conditional statements;

Comments for PHP

1.//

2.#

3./* * *

Variable

A variable is a container for storing information;

Variable rule:

1. The variable begins with $, followed by the name "" $sum;

2. The variable must begin with a letter or a slide, and cannot begin with a number;

3. Variable name is case-sensitive "" $q is not the same as $q;

PHP Data type

Four types of scalar:

1.Boolean (Boolean) "True False;

2.Integer (integral type) "" No decimal number, plus or minus can be;

3.Float (floating point type) "There is a decimal or exponential form of existence;

4.String (String) "text";

The difference between a php single quote and a double quote

1. "" Will analyze if there is a variable, if there is a variable to parse the variable and then output the string;

2. "Direct output string;

PHP Two types of composite

1.array (array) stores multiple values in a variable; $arr =array (...)

2.object (object) objects are data types that store data and about how the data is processed;

Two special types of PHP

1.resource (resources);

2.NULL;

PHP Constants

Constants are identifiers of a single value, beginning with a character or underscore;

Define (' Constant name ', ' value ', false/true) ' false does not distinguish between constant name case, true distinction;

The PHP operator

+-*/%;

Assignment operators

1. $x = $y "" Assigns the value of Y to X;

2. $x + = $y "" $x = $x + $y;

3. $x-= $y;

4. $x *= $y;

PHP character Join operation

1.. connector;

2. = Assignment Link "" $a = ' xxxx '; $b = ' yyy '; $a. = $b; $a = ' xxxyyy ';

PHP Increment decrement operator

+ + $x before incrementing $x plus 1 increments and then returns $x;

$x + + after the increment first return $x and then add 1 increment;

--Diminishing before $x;

$x--diminishing after;

PHP comparison Operators

= = equals $x = = $y;

= = = Congruent (exactly the same, the same type);

!== not congruent (completely different);

! = range;

<> range;

> Greater than;

< less;

>= is greater than or equal to;

<= less than or equal to;

PHP logical operators

and with;

Or or $x or $y at least one is true to return true;

XOR is different or has only one and has a true return true;

&& and;

|| Or

! No! $x returns True if $x is not true;

PHP conditional statements

if (condition)

{

...... Meet the conditions of implementation;

}

Else

{

...... Do not meet the conditions of implementation;

}

Switch ()

{

Case ():

...... ；

Break

Default

......;

}

PHP comments, variables, types, constants, operators, comparators, conditional statements;