Detailed example of the usage of foreach in php

1. What is foreach?

foreach is a grammatical structure of PHP. It is actually a tool (tool: a tool used when working). In the process of program development, in order to achieve program effects, use Arrived foreach.

2. How to use?

Official:

foreach (array_expression as $value)
statement
foreach (array_expression as $key => $value)
statement

Example:

$arr = array(1,2,3,4);//定义数组
foreach ($arr as &$value) {
    $value = $value*2;//循环遍历并修改数组中的值
}
echo "<pre class="brush:php;toolbar:false">";
print_r($arr);//打印输出最终结果

Result: (&$value is a reference assignment)

　　Array
　　(
    　　[0] => 2
  　　  [1] => 4
   　　 [2] => 6
   　　 [3] => 8
　　)

Example:

    $a = array(
    "one" => 1,
    "two" => 2,
    "three" => 3,
    "seventeen" => 17
);
 
foreach ($a as $k => $v) {
    echo "<pre class="brush:php;toolbar:false">";
    echo "[$k] => $v\n";
}

Result:

[one] => 1
[two] => 2
[three] => 3
[seventeen] => 17

Explanation: k actually refers to key, v actually refers to value
Summary: foreach is frequently used in PHP projects, especially when processing Array time!

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