1. Constant
After the constant value is defined, is not to be changed at any elsewhere in the script, a constant consists of letters, underscores, and numbers, but the numbers can not appear as the first letter. (Constant names do not need to add $ modifier).
Note: Constants can be used throughout the script.
Setting constants, using the define () function, the function has the following syntax: BOOL DEFINE ( String $ name , Mixed value $ [, BOOL $ CASE_INSENSITIVE = to false ] )
The function takes three parameters: name:Required parameters constant names, i.e., identifiers. value:Required parameter values, constants. CASE_INSENSITIVE : optional parameter, if set to TRUE, this constant is not case sensitive. The default is case-sensitive.
Example:
<div class = "Box">
<PHP?
the DEFINE ( 'LIANG', 'Welcome to the PHP world'); // If the third argument without default is false
echo LIANG; // output: Welcome to the PHP world
echo '<br>';
echo Liang; // output: liang because case-sensitive, so LIANG not recognize this constant defaults to echo a content
>?
</ div>
<div class = "Box">
<PHP?
define ( 'LIANG', 'Welcome to the PHP world', to true);
echo LIANG; // output: Welcome to the world PHP
echo '<br>';
echo Liang; // output: Welcome to the world PHP
// the above is provided as a third parameter is true, so here is not case sensitive, it is possible to identify constant LIANG
?>
</ div>
After defining the constants, the default is a global variable can be used anywhere in the entire run of the script. Even constants defined may be outside a function in the function of normal use constants.
Such as:
<div class="box">
<?php
define("hermit", 'php,你好！', true);
function hua(){
echo hermit;
}
hua (); // output php, hello!
?>
</ Div>
2. string variable
String variable for storing and processing the text. A character string variable with a value. After you create a string we can manipulate it up. You can use directly in a function string, or store it in a variable.
3. The concatenation operator
In PHP, there is only one string operator. Concatenation operator (.) Is used to connect the two string values.
如：<div class="box">
<? PHP
$ text1 = "Welcome";
$ text2 = "came to the PHP world!";
. $ echo $ text1 text2;
?>
</ div>
4. strlen () function
Sometimes you know the length of the string value is useful. strlen () function returns the length of the string (number of characters). strlen () is often used in the cycle and other functions.
Such as:
<div class = "Box">
<PHP?
$ text3 = "Liang Tuhua"; // Note that spaces are also considered a position
echo strlen ($ text3); // output: 11
?>
</ div>
5.strpos () function
the strpos () function is used to find a character string or within a specified text. If a match is found in the string, the function returns a match for the first character position (subscript). If a match is not found, FALSE is returned.
Such as: ? <PHP
text4 = $ "Liang Tuhua";
echo strpos ($ text4, "Tuhua"); // output 6, starting at index 0, including spaces
>?
6. Operator
1. Arithmetic Operators
+ (Addition) - (subtraction) * (multiplication) / (division) % (modulus, also known as remainder) (juxtaposed).
PHP7 + version of the new operator divisible intdiv () , such as:
2. assignment operator
= (Assignment) + = (plus etc.) - = (minus the like) * = (multiplication, etc.) / = (except the like) % = (mold etc.) = (and the like). Example: a = b = A corresponds. a. b
3. increment / decrement operators
++ i (pre-increment, I before adding 1, then return to I) I ++ (post-increment, the first return I , in I plus 1 ) Inc. (www.i-levelmedia.com) (pre-decrement, I is decremented by 1 first, and then returns I ) I - ( after descending, first return to I , I is decremented by 1 in )
4. Comparison Operators
== (equal) === (absolute equal to) ! = (Not equal to) <> (not equal to) ! == (absolutely not equal) > (greater than) <(less than) > = (greater than or equal to) <= ( less)
The logical operators
a and b (and also known as and) if a and b are true, then returns to true a or b (or a) if a and b have at least one true, then returns to true a XOR b (XOR) if a and b and only one is true, return true
a && b (and also known and) if a and b are true, then return TRU E a || b (or a)if at least one of a and b is true, then returns to true! a (non) if a is not true, return true
6. The ternary operator (also called operation trinocular)
(expr1) ? (expr2) : (expr3)
Expr1 expr2 is evaluated for the time is TRUE, the value at the time of expr3 expr1 evaluates FALSE. Since PHP 5.3 onwards, the ternary operator can omit the intermediate portion. Expression expr1:? Expr3 returns expr1 when expr1 evaluates to TRUE, otherwise returns expr3.
7. The combination of comparison operators (PHP7 +)
PHP7 + comparison operator support composition (combined comparison operator), also known spacecraft operator, symbol <=> . Comparison operator can easily compare the combination of two variables, of course, not limited to the value of class data comparison.
If $ a> $ b, $ c is a value of 1. If $ a == $ b, $ c is a value of 0. If $ a <$ b, $ c is a value of -1.
Such as: Note: Use the accident report will appear in php '>' error on the version of less than PHP7 ,
$a = 8;
$b = 5;
$c = $a <=> $b;
echo: $ c; // Output 1
8. Operator Priority
9. the If ... Else statement
if statement - execute code when conditions are met
if ... else statement - execute code when a condition is satisfied, another piece of code is executed when the condition is not satisfied
if ... elseif .... else statement - execute a block of code // when one of several conditions are met elseif and else if the effect is the same, elseif is PHP is else if a special edition achieve fault tolerance. Strict wording for the latter: the else IF
switch statement - execute a block of code when one of several conditions are met
Such as: the use of javascript and the same.
? <PHP
$ = n-2;
Switch (n-$) {
Case. 1:
echo "two. 1";
BREAK;
Case 2:
echo "three 2";
BREAK;
Case liang3:
echo "four. 3";
BREAK;
default:
echo "no number";
}
>?