How to use For loop and Foreach loop in PHP (detailed picture and text explanation)

In the previous article, I brought you "How to figure out PHP's While loop and do-while loop, five minutes is enough! ", this article introduces in detail how to use and distinguish PHP's While loop and do-while loop. This article continues to bring you the other two loop statements in PHP, about PHP's for Loops and foreach loops. Hope it helps everyone!

for loop and foreach loop in PHP

• For loop

The syntax and logic format of the for loop is a bit different from the while and do while loop statements we saw before. The for loop predefines the variable that controls the number of loops in the for statement. The for loop is mostly used when the number of times the loop needs to run is known in advance.

The syntax format of the For loop is as follows:

for (初始表达式; 表达式条件判断; 变量更新) {
    循环动作;
}

Initialization expression: It is an initialization assignment. Multiple codes can be assigned at the same time. It is usually used to declare the initial value of a counter. .

Expression condition judgment: used to control whether to execute the code in the loop body, which is the restriction condition of loop execution; if the judgment condition value is TRUE, the loop will continue and the loop statement will be executed. If the judgment condition value is FALSE, the loop is terminated.

Variable update: Update the variable each time the loop is executed to proceed to the next loop.

The example is as follows:

<?php
for($a=1;$a<5;$a++){
    echo "输出结果是：".$a."<br/>";
}
?>

Output result:

##The for loop can not only execute one condition, but also multiple Conditions, examples are as follows:

<?php
 for($a=0,$b=5;$a<=5;$a++,$b--){
     echo $a  ."和" .$b ."<br/>";
 }
 ?>

Output results:

for loop statements can also be nested together like while statements. , that is, the for loop statement contains another one or more for loop statements. We can use this method of for loop to output the multiplication table we learned in elementary school. The example is as follows:

<?php
 for($a = 1 ; $a < 10 ; $a++ ){
     for($b=1;$b<=$a;$b++){
        echo $b . &#39;x&#39; . $a . &#39;=&#39; .($a*$b) . &#39;   &#39;;//&nbsp输出的是空格
     }
     echo &#39;<br />&#39;;
 
 }
 ?>

Output result:

• foreach loop
  

PHP’s foreach loop structure is commonly used when traversing arrays method.

The syntax format of the foreach loop is as follows:

foreach( 要循环的数组变量 as [键变量 =>] 值变量){
//循环的结构体
}

This usage is fixed, put the array that needs to be looped.

as As a fixed keyword, the following key variable is optional. You can define a variable at will. Every time it loops, the foreach syntax will take out the key and assign it to the key variable. The following Value variable is required. Each time it loops, the value is placed in the value variable.

The examples are as follows:

<?php
$a = array(
    &#39;键名1&#39; => &#39;值1&#39;,
    &#39;键名2&#39; => &#39;值2&#39;,
);
foreach($a  as $key => $value){
    echo $key . &#39;对应&#39; . $value . &#39;<br />&#39;;
}
?>

Output results:

## Recommended learning: "

PHP Video Tutorial

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