PHP basic loop control statement study notes-PHP Tutorial-php.cn

Home

Backend Development

PHP Tutorial

PHP basic loop control statement study notes

伊谢尔伦

Jun 22, 2017 am 10:19 AM

php Base study cycle control statement

LoopControl statement

Conditional control statement, you can choose to execute different statements based on conditions. But sometimes you need to reuse a certain piece of code or function.

while loopStatement

While loop is the simplest loop statement in PHP. Its syntax format is:

while(expr){
     statement;
}

Copy after login

whenExpressionWhen the value of expr is true, the statement statement will be executed. After the execution is completed, it will return to the expr expression to continue judgment. Until the value of the expression is false, the loop is broken out and the following statement is executed.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"/>
<title>PHP语言基础</title>
</head>
<body>
<?php
header("Content-Type:text/html;   charset=gb2312");
$num=1;
$str="10以内的偶数为:";
while($num <= 10){
     if($num % 2 == 0){
          $str.=$num." ";
     }
     $num++;
}
echo $str;

?>
</body>
</html>

Copy after login

Running results:
Even numbers within 10 are: 2 4 6 8 10

do...while loop statement

There is another form of while statement means, that is, do...while. The difference between the two is that do...while loops one more time than the while statement. When the value of the while expression is false, the while loop jumps out of the current loop directly; while the do...while statement executes the program block first and then judges the conditional expression.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"/>
<title>PHP语言基础</title>
</head>
<body>
<?php
header("Content-Type:text/html;   charset=gb2312");
$num=1;
while($num != 1){
     echo "不会看到";
}

do{
     echo "会看到";
}while($num != 1);

?>
</body>
</html>

Copy after login

Running results:
You will see

for loopStatement

The for loop is the most complex loop structure in PHP. The syntax format is:

for(expr1;expr2;expr3){
   statement;
}

Copy after login

Among them, expr1 takes a value unconditionally during the first loop; expr2 is evaluated before the start of each loop. If the value is true, the statement is executed, otherwise, jump out of the loop and continue. executed; expr3 is executed after each loop.

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"/>
<title>PHP语言基础</title>
</head>
<body>
<?php
header("Content-Type:text/html;   charset=gb2312");
$num=1;
for($i=1;$i <= 100;$i++){
     $num*=$i;
}
echo "100!=".$num;
?>
</body>
</html>

Copy after login

Run result:
100!=9.3326215443944E+157

foreach loop statement

The foreach loop was introduced in PHP4 and can only be used for arrays. In PHP5, support for objects has been added. Syntax format:

foreach(array_expression as $value)
     statement;

Copy after login

foreach(array_expression as $key => $value)
     statenment;

Copy after login

<!DOCTYPE html >
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"/>
<title>PHP语言基础</title>
</head>
<body>
<?php
header("Content-Type:text/html;   charset=gb2312");
$name=array("1"=>"Jack","2"=>"Ben","3"=>"Bill");
foreach($name as $key => $value){
     echo " ".$name[$key];
}
?>
</body>
</html>

Copy after login

Running result:
Jack Ben Bill

Another writing format for process control

In a complex PHP page, it may contain multiple conditional control statements, loop control statements and functions. It is very troublesome to just find matching braces "{}". For this purpose, PHP provides another writing format, including if, while, for, foreach and switch. The basic form of writing format is: use colon ":" to replace the left brace "{"; use endif;, endwhile, endfor, endforeach; and endswitch; to replace the right brace "}".

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"/>
<title>PHP语言基础</title>
</head>
<body>
<?php
header("Content-Type:text/html;   charset=gb2312");
$ss=2;
$max=1000;
$arr=array();
echo $max."以内的素数为：";
while($ss < $max):
     $boo=false;
     foreach($arr as $value):
          if($ss % $value ==0):
               $boo=true;
               break;
          endif;
     endforeach;
     if(!$boo):
          echo $ss." ";
          $arr[count($arr)]=$ss;
     endif;
     $ss++;
endwhile;
?>

</body>
</html>

Copy after login

Operation results:
The prime numbers within 1000 are: 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101 103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191 193 197 199 211 223 227 229 233 239 241 251 257 263 269 271 277 281 283 29 3 307 311 313 317 331 337 347 349 353 359 367 373 379 383 389 397 401 409 419 421 431 433 439 443 449 457 461 463 467 479 487 491 499 503 509 521 523 541 547 557 563 569 571 577 587 593 599 601 607 61 3 617 619 631 641 643 647 653 659 661 673 677 683 691 701 709 719 727 733 739 743 751 757 761 769 773 787 797 809 811 821 823 827 829 839 853 857 859 863 877 881 883 887 907 911 919 929 937 941 947 95 3 967 971 977 983 991 997

Use break/continue Statement to jump out of the loop

When using a loop statement, sometimes the number of loops is uncertain. In this case, you can use an infinite loop, such as:

while(true){     ...}

Copy after login

for(;;){     ...}

Copy after login

Only when the program block meets certain conditions will it break out of the loop. The keywords used to break out of the loop are break and continue.

The break keyword can terminate the current loop, including all control statements including while, do...while, for, foreach and switch.
The break statement can not only jump out of the current loop, but also specify how many levels of loops to jump out of. The format is:

break $num;

Copy after login

Parameter $num specifies how many levels of loops to jump out of.

The continue keyword is not as powerful as break. Continue can only terminate this loop and enter the next loop. Continue can also specify how many loops to jump out of.

The above is the detailed content of PHP basic loop control statement study notes. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress images for free

Clothoff.io

AI clothes remover

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

R.E.P.O. Best Graphic Settings

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Assassin's Creed Shadows: Seashell Riddle Solution

2 weeks ago By DDD

R.E.P.O. How to Fix Audio if You Can't Hear Anyone

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

WWE 2K25: How To Unlock Everything In MyRise

1 months ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

Where is the login entrance for gmail email?

7505

CakePHP Tutorial

1378

What is the format of the account name of steam

win11 activation key permanent

nyt connections hints and answers

Related knowledge

PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian Dec 24, 2024 pm 04:42 PM

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

How To Set Up Visual Studio Code (VS Code) for PHP Development Dec 20, 2024 am 11:31 AM

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

How do you parse and process HTML/XML in PHP? Feb 07, 2025 am 11:57 AM

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

PHP Program to Count Vowels in a String Feb 07, 2025 pm 12:12 PM

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Apr 05, 2025 am 12:04 AM

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

7 PHP Functions I Regret I Didn't Know Before Nov 13, 2024 am 09:42 AM

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

Explain late static binding in PHP (static::). Apr 03, 2025 am 12:04 AM

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? Apr 03, 2025 am 12:03 AM

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

See all articles