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HomeBackend DevelopmentPHP TutorialNotes on the basic syntax structure of PHP loop statements_PHP tutorial

Notes on the basic syntax structure of PHP loop statements_PHP tutorial

Jul 13, 2016 am 10:50 AM
forforeachphpexistBasiccyclenotesstatementGrammatical structures

There are many loop statements in PHP, such as: for, foreach, while, do while, goto statements. Let me briefly introduce the usage of these loop statement structures.

for loop control

for(initial value of loop; condition of loop; step size){
                         
//Execute statement;

}

Example

The code is as follows Copy code
 代码如下 复制代码

FOR ($i = 0; $i {
print "value is now " . $i . "
";
}

FOR ($i = 0; $i { print "value is now " . $i . "
";

}


Output value

value is now 0

value is now 1

value is now 2

In the first loop, $i=0, which means that the expression, ($i

In the second loop, $ = 1, which means that the expression, ($i

In the third iteration, $i= 2, which means that the expression, ($i In the fourth iteration, $i= 3, which means the expression, ($i

while loop



The basic grammatical structure is

while(loop condition){
       

//Execute statement;

//The loop condition value changes. If it is not added, it will become an infinite loop

 代码如下 复制代码


";  $a++;  }?>
}

Example

The code is as follows Copy code

"; $a++; }?>

Let’s take a simple example and you’ll understand it at a glance. The following example uses a while loop statement. It means that when the variable $a is less than or equal to 5, a loop is executed. The loop executes two statements. One is to output the value of $a, and the other is to give $a Add 1 to the value, and stop looping until $a is less than or equal to 5 and is FALSE, that is, $a > 5.

do..while loop control

Basic grammatical structure

do{

//Execute statement;

//The loop condition value changes. If it is not added, it will become an infinite loop
 代码如下 复制代码


";  }while ($i
}while(loop condition); Example The example is as follows. In this example, a loop is first executed, that is, $i is increased by 1, and then the value of $i is output. After executing the first loop, the condition $i
The code is as follows Copy code
"; }while ($i


Loop related statements-break

Basic concept: Indicates the end of the current for, while, do..while, switch, process. You can give a number to indicate which layer to exit to.

1. The break statement will jump out to level 1 by default

2. The number after the break statement cannot exceed the actual number of loop levels that can be jumped out, otherwise, a fatal error will be reported

Loop-related statements-continue

Basic concept: continue is used to end the remaining code of this loop and start a new loop from scratch (if the condition is true, continue execution), continue can also be followed by a number to indicate the number of loops to restart from

goto statement

Basic concept: Through the goto statement, we can jump the program to a specified place for execution.

goto tag;

Tag:

Statement;

Quick Start Case:

3. When a constant is defined, it needs to be assigned an initial value.
The code is as follows
 代码如下 复制代码

goto a;

echo 'aa';

a:

echo 'bb';

Copy code



goto a;

echo 'aa';

a:

echo 'bb';

Constant in php

Description:

The so-called constants, we can understand that achievements are special variables: reflected in

1. You don’t need $ before defining a constant

2. Once a constant is defined, its value cannot be modified
 代码如下 复制代码


       //第一种方法

       define("TAX_RATE",0.08);
       echo TAX_RATE;

       //第二种方法(php5.3)

       const TAX_RATE2=0.1;
       echo '-'.TAX_RATE2;

?>

4. Constants can be defined or const

5. The name of the constant, we generally say it is all capital letters, and then separated by underscores

Quick Start Case:
The code is as follows Copy code
//The first method define("TAX_RATE",0.08);
echo TAX_RATE;
//Second method (php5.3) const TAX_RATE2=0.1; echo '-'.TAX_RATE2; ?> http://www.bkjia.com/PHPjc/632629.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632629.htmlTechArticleThere are many loop statements in PHP, such as: for, foreach, while, do while, goto statements, Let me give you a brief introduction to the usage of these loop statement structures. for loop control for(loop...
Statement
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