Android programmers learn PHP development (19)-Basic concepts and definitions of arrays (1)-PhpStorm

<?php
    /**
     * 数组
     * 直接赋值声明数组，如下：
     * $arr = array("one"=>"111111","two"=>"222222");
     * 其中，one、two是key（键名），111111、222222是value（值、也叫键值）
     */

    echo "---------- 索引数组 : 下标是整数 ----------<br>";
    $arr[0] = 1;
    $arr[1] = 2;
    $arr[2] = 3;
    print_r($arr); // 打印结果：Array ( [0] => 1 [1] => 2 [2] => 3 )
    echo "<br>";

    echo "---------- 关联数组 : 下标是字符串 ----------<br>";
    $arr1[&#39;one&#39;] = 1;
    $arr1[&#39;two&#39;] = 2;
    $arr1[&#39;three&#39;] = 3;
    print_r($arr1); // 打印结果：Array ( [one] => 1 [two] => 2 [three] => 3 )
    echo "<br>";

    echo "---------- 数组 Demo ----------<br>";
    $arr2 = $arr + $arr1;
    print_r($arr2);
    echo "<br>";

    echo "---------- 数组 Demo 2 ----------<br>";
    $arr3[] = 1;
    $arr3[] = 2;
    $arr3[] = 3;
    $arr3[] = 4;
    print_r($arr3);
    echo "<br>";

    /**
     *     <pre class="brush:php;toolbar:false">标签 函数的结果格式化输出，即，按原型打印。阅读起来就比较方便。
     *     echo &#39;<pre class="brush:php;toolbar:false">&#39;;
     *     print_r($arr);
     *     echo &#39;

'; */ echo "---------- 数组 Demo 3 ----------
"; $arr4 = array(); for ($i=0; $i<10; $i++){ $arr4[] = $i * $i; } echo '

';
    print_r($arr4);
    echo '

'; /* 打印结果： Array ( [0] => 0 [1] => 1 [2] => 4 [3] => 9 [4] => 16 [5] => 25 [6] => 36 [7] => 49 [8] => 64 [9] => 81 ) */ echo "---------- 数组 Demo 4 ----------
"; $arr5 = array(); for ($i=0; $i<10; $i++){ //echo $i."
"; if ($i == 4){ $arr5['刘德华'] = "欧巴"; } if ($i == 7){ $arr5[-100] = 6666; } $arr5[] = $i * $i; } echo '

';
    print_r($arr5);
    echo '

'; /* 打印结果： Array ( [0] => 0 [1] => 1 [2] => 4 [3] => 9 [刘德华] => 欧巴 [4] => 16 [5] => 25 [6] => 36 [-100] => 6666 [7] => 49 [8] => 64 [9] => 81 ) */ /** * 以下是几种定义数组的方式： */ echo "---------- 数组 Demo 5 ----------
"; $arr6 = array(1,2,3,4,5,6); $arr7 = array("one","two","three"); $arr8 = array(0=>"aaa",1=>"bbb",2=>"ccc"); $arr9 = array("aaa",6=>"bbb","ccc"); $arr10 = array("name"=>"wang","age"=>20);