blocks|key|2284136|text|你的循环运行了五次。每次通过循环，您都会将10添加到$a的值中。做五次就有50次了。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2284137|entityMap^0|Q|2|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Your loop runs five times. Each time through the loop you add 10 to the value of <code>$a</code>. Doing that five times gives you 50.

blocks|key|1170321|text|从$i=0开始，然后做$a%2B10和$b%2B5，就像$i+<5一样|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1170322|$i=0,+$a=10,+$b=5

$i=1,+$a=20,+$b=10

$i=2,+$a=30,+$b=15

$i=3,+$a=40,+$b=20

$i=4,+$a=50,+$b=25|code-block|syntax|javascript|1170323|$i=5，现在循环停止了，因为$i+is+no+longer+<5|1170324|entityMap^0|1|4|B|5|H|4|O|5|0|0|0|4|F|I|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|N|$]]

You start with <code>$i=0</code>, then you do <code>$a+10</code> and <code>$b+5</code> as long as <code>$i &lt;5</code>

<pre><code>$i=0, $a=10, $b=5

$i=1, $a=20, $b=10

$i=2, $a=30, $b=15

$i=3, $a=40, $b=20

$i=4, $a=50, $b=25
</code></pre>

<code>$i=5</code>, now the loop stops because <code>$i is no longer &lt;5</code>

blocks|key|1531630|text|这就是它的工作方式。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1531631|假设你没有钱。我告诉你，每次你做5件家务，我都会给你一美元。不过，我只给你5美元。一开始你没有钱，一次杂务之后，我给你5美元。现在你有5美元了。你再做一次家务，我再给你5次，使你达到10次。我现在给了你两美元。我再给你5块--你有15块。我给你另外一份--+20美元--再给你一份；给你25美元。现在我已经给了你我的限额，我们的循环已经完成了。|1531632|在这个故事中，我的美元是你的$i价值。从0开始，工作到5。你的家务是你的$b值，它每次都被添加到你的工作中。|offset|length|style|CODE|1531633|代码示例：|1531634|for+($dollars=0;+$dollars+<+5;+$dollars%2B%2B)+{+
++++$chores+%2B=+5;
}|code-block|syntax|javascript|1531635|entityMap^0|0|0|E|2|10|2|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|U|8|@$F|V|G|W|H|I]|$F|X|G|Y|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|Z|8|@]|9|@]|A|$]]|$1|L|3|M|5|N|7|10|8|@]|9|@]|A|$O|P]]|$1|Q|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|R|$]]

This is the way it works.

Let's say you have a no dollars. And I tell you that I will give you a dollar everytime you do 5 chores. However, I will only give you 5 dollars. At first you have no dollars and after one chore I give you 5 dollars. Now you have 5 dollars. You do another chore and I give you another 5, bringing you to ten. I have now given you two dollars. I give you another 5 - you have 15. I give you another - 20 - and one more; bringing you to 25 dollars. Now I have given you my limit of dollars, and our loop is complete.

In this story, my dollars are your <code>$i</code> value. Beginning at 0, working up to 5. Your chores are your <code>$b</code> values, which are added to every time.

Code example:

<pre><code>for ($dollars=0; $dollars &lt; 5; $dollars++) { 
 $chores += 5;
}
</code></pre>

blocks|key|1531676|text|%2B=不增加它的赋值运算符。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1531677|http://php.net/manual/en/language.operators.assignment.php|offset|length|1531678|正如我在评论中提到的，以及其他人在回答中提到的。%2B=将向右边的值添加到左边的值。所以在一个循环中它是这样的|1531679|步骤0+$a+=5(+0%2B5)|unordered-list-item|1531680|步骤1+$a+=+10+(5次前迭代退出value%2B5+)|1531681|步骤2+$a+=+15+(先前迭代退出值%2B+5)|1531682|等等..。|1531683|值得注意的是，您还可以执行-=、*=等操作和.=操作，或者追加所有相同的操作。|style|CODE|1531684|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1M|0|0|0|0|0|0|0|D|2|G|2|M|2|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@]|9|@$D|13|E|14|1|15]]|A|$]]|$1|F|3|G|5|6|7|16|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|17|8|@]|9|@]|A|$]]|$1|K|3|L|5|J|7|18|8|@]|9|@]|A|$]]|$1|M|3|N|5|J|7|19|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1A|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1B|8|@$D|1C|E|1D|S|T]|$D|1E|E|1F|S|T]|$D|1G|E|1H|S|T]]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|C]]]]

+= is not increment its an assignment operator.

<a href="http://php.net/manual/en/language.operators.assignment.php" rel="nofollow">http://php.net/manual/en/language.operators.assignment.php</a>

As I mentioned in the comments, and others in their answers. += will add the value to on the right to the value on the left. so in a loop its like this

<ul>
<li>step 0 $a = 5 ( 0+5)</li>
<li>step 1 $a = 10 (5[previous iteration exit value]+5 ) </li>
<li>step 2 $a = 15 (10[previous iteration exit value] + 5) </li>
</ul>

so on....

Of note is you can also do <code>-=</code> <code>*=</code> etc. and <code>.=</code>or append all the same kind of operation.

blocks|key|1170379|text|当您知道要执行语句或语句块的次数时，会使用for语句。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1170380|​|1170381|📷|atomic|offset|length|1170382|1170383|语法：|style|BOLD|1170384|for+(initialization;+condition;+increment){
+++code+to+be+executed;
}|code-block|syntax|javascript|1170385|初始化器用于设置循环迭代次数的计数器的起始值。为此目的，可以在这里声明一个变量，将其命名为$i是传统的做法。|CODE|1170386|示例|1170387|下面的示例进行五次迭代，并在循环−的每次传递中更改两个变量的赋值|1170388|<html>
+++<body>

++++++<?php
+++++++++$a+=+0;
+++++++++$b+=+0;

+++++++++for(+$i+=+0;+$i<5;+$i%2B%2B+)+{
++++++++++++$a+%2B=+10;
++++++++++++$b+%2B=+5;
+++++++++}

+++++++++echo+("At+the+end+of+the+loop+a+=+$a+and+b+=+$b"+);
++++++?>

+++</body>
</html>|1170389|这将产生以下结果−|1170390|At+the+end+of+the+loop+a+=+50+and+b+=+25|1170391|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://developer.qcloudimg.com/http-save/yehe-900000/049530879689176a8681f64675f94119.jpg|imageAlt^0|0|0|0|1|0|0|0|0|3|0|0|19|2|0|0|2|0|0|0|0|0|14|0^^$0|@$1|2|3|4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1F|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1G|8|@]|9|@$G|1H|H|1I|1|1J]]|A|$]]|$1|I|3|C|5|6|7|1K|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|1L|8|@$G|1M|H|1N|L|M]]|9|@]|A|$]]|$1|N|3|O|5|P|7|1O|8|@]|9|@]|A|$Q|R]]|$1|S|3|T|5|6|7|1P|8|@$G|1Q|H|1R|L|U]]|9|@]|A|$]]|$1|V|3|W|5|6|7|1S|8|@$G|1T|H|1U|L|M]]|9|@]|A|$]]|$1|X|3|Y|5|6|7|1V|8|@]|9|@]|A|$]]|$1|Z|3|10|5|P|7|1W|8|@]|9|@]|A|$Q|R]]|$1|11|3|12|5|6|7|1X|8|@]|9|@]|A|$]]|$1|13|3|14|5|6|7|1Y|8|@$G|1Z|H|20|L|U]]|9|@]|A|$]]|$1|15|3|-4|5|6|7|21|8|@]|9|@]|A|$]]]|16|$17|$5|18|19|1A|A|$1B|1C|1D|-4]]]]

The for statement is used when you know how many times you want to execute a statement or a block of statements.

<a href="https://i.stack.imgur.com/0ZWxO.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0ZWxO.jpg" alt="enter image description here"></a>

Syntax:

<pre><code>for (initialization; condition; increment){
 code to be executed;
}
</code></pre>

The initializer is used to set the start value for the counter of the number of loop iterations. A variable may be declared here for this purpose and it is traditional to name it <code>$i</code>.

Example

The following example makes five iterations and changes the assigned value of two variables on each pass of the loop −

<pre><code>&lt;html&gt;
 &lt;body&gt;

 &lt;?php
 $a = 0;
 $b = 0;

 for( $i = 0; $i&lt;5; $i++ ) {
 $a += 10;
 $b += 5;
 }

 echo ("At the end of the loop a = $a and b = $b" );
 ?&gt;

 &lt;/body&gt;
&lt;/html&gt;
</code></pre>

This will produce the following result −

<code>At the end of the loop a = 50 and b = 25</code>

blocks|key|2284327|text|For+loop是入口条件循环。它首先对条件进行评估，这样即使条件不能满足，与循环关联的语句块也不会运行一次。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2284328|这个for循环块中的语句将运行5次，$i的值为0到4；假设循环是单独运行的。|2284329|+$a=0;
+$b=0;
+for+($i+=+0;+$i+<+5;+$i%2B%2B){
+++++++echo+$a+%2B=+10;
+++++++echo+' ';
+}|code-block|syntax|javascript|2284330|输出的是这样的。|BOLD|2284331|10
20
30
40
50|2284332|现在又是一个循环|2284333|for+($i=0;+$i+<+5;+$i%2B%2B)+{+
++++++echo++$b+%2B=+5;
++++++echo+' ';

+}|2284334|输出的如下所示|2284335|5
10
15
20
25|2284336|在每次迭代中，它都使用10和5将赋值算子x+%2B=+y添加到以前的迭代次数中。|2284337|entityMap|0|LINK|mutability|MUTABLE|url|http://www.w3schools.com/php/php_operators.asp^0|0|8|0|0|0|0|3|0|0|0|0|0|3|0|0|B|2|E|1|G|A|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1C|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1D|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1E|8|@$9|1F|A|1G|B|O]]|D|@]|E|$]]|$1|P|3|Q|5|J|7|1H|8|@]|D|@]|E|$K|L]]|$1|R|3|S|5|6|7|1I|8|@]|D|@]|E|$]]|$1|T|3|U|5|J|7|1J|8|@]|D|@]|E|$K|L]]|$1|V|3|W|5|6|7|1K|8|@$9|1L|A|1M|B|O]]|D|@]|E|$]]|$1|X|3|Y|5|J|7|1N|8|@]|D|@]|E|$K|L]]|$1|Z|3|10|5|6|7|1O|8|@$9|1P|A|1Q|B|C]|$9|1R|A|1S|B|C]]|D|@$9|1T|A|1U|1|1V]]|E|$]]|$1|11|3|-4|5|6|7|1W|8|@]|D|@]|E|$]]]|12|$13|$5|14|15|16|E|$17|18]]]]

<code>For loop</code> is entry condition loop. It evaluate condition first, so the statement block associated with the loop won't run even once if the condition fails to meet

The statements inside this for loop block will run 5 times, the value of $i will be 0 to 4;
Imagine the loops are running separately.

<pre><code> $a=0;
 $b=0;
 for ($i = 0; $i &lt; 5; $i++){
 echo $a += 10;
 echo '&lt;br&gt;';
 }
</code></pre>

And the output like this.

<pre><code>10
20
30
40
50
</code></pre>

Now another Loop

<pre><code>for ($i=0; $i &lt; 5; $i++) { 
 echo $b += 5;
 echo '&lt;br&gt;';

 }
</code></pre>

And the output like this

<pre><code>5
10
15
20
25
</code></pre>

In each iteration it adds <code>10</code> and <code>5</code> to previous number of iteration using the <a href="http://www.w3schools.com/php/php_operators.asp" rel="nofollow">assignment operator x += y</a>.

I'm a newbie to php and I've understood all other loops in php but the question is I cannot understand how the for loops works for ex:
Here is the code;

<pre><code>$a = 0;
$b = 0;

for ($i=0; $i &lt; 5; $i++) { 
 $a += 10;
 $b += 5;
}
echo("At the end of the loop a=$a and b=$b");
</code></pre>

When I execute this script the value of a = 50 and b = 25! 

<blockquote>
 Is it multiplying the a value with i's increment value? like 10 * 5 = 50.
</blockquote>

How does for loop works actually in php?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我是php的新手，我已经理解了php中的所有其他循环，但问题是，我无法理解for循环是如何工作的，用于ex:这是代码；$a = 0;$b = 0;for ($i=0; $i < 5; $i++) { $a += 10; $b += 5;}echo("At the end of the loop a=$a and b=$b");当我执行这个脚本时，a= 50和b= 25的值！它是将a值

问for循环是如何在php中实际工作的？
EN

回答 6

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