开源达人最近项目开发中对于while循环总结了一个demo

<?php

echo “========== while 循环基础示例 ==========\n”;

// 示例1: 基础计数循环

echo “示例1: 基础计数 (1到10)\n”;

$i = 1;

while ($i <= 10) {

    echo “$i “;

    $i++;

}

echo “\n\n”;

//=================================================

// 示例2: 条件判断循环

echo “示例2: 用户输入模拟\n”;

$continue = true;

$attempt = 1;

while ($continue && $attempt <= 3) {

    echo “尝试次数: $attempt\n”;

    // 模拟某种条件判断

    if ($attempt == 2) {

        $continue = false;

        echo “条件满足，退出循环\n”;

    } else {

        echo “继续循环…\n”;

    }

    $attempt++;

}

echo “\n”;

//=================================================

// 示例3: 数组遍历

echo “示例3: 遍历数组元素\n”;

$fruits = [“苹果”, “香蕉”, “橙子”, “葡萄”, “草莓”];

$index = 0;

while ($index < count($fruits)) {

    echo “索引 $index: {$fruits[$index]}\n”;

    $index++;

}

echo “\n”;

//=================================================

// 示例4: 数值计算

echo “示例4: 计算1到100的和\n”;

$sum = 0;

$num = 1;

while ($num <= 100) {

    $sum += $num;

    $num++;

}

echo “1到100的和为: $sum\n\n”;

//=================================================

// 示例5: 字符串处理

echo “示例5: 字符串处理\n”;

$text = “Hello”;

$position = 0;

while ($position < strlen($text)) {

    echo “位置 $position 的字符: {$text[$position]}\n”;

    $position++;

}

echo “\n”;

//=================================================

// 示例6: 嵌套while循环

echo “示例6: 嵌套循环 – 打印乘法表的一部分\n”;

$row = 1;

while ($row <= 3) {

    $col = 1;

    echo “第 $row 行: “;

    while ($col <= 3) {

        echo ($row * $col) . ” “;

        $col++;

    }

    echo “\n”;

    $row++;

}

echo “\n”;

//=================================================

// 示例7: 与您二分查找类似的while循环

echo “示例7: 模拟二分查找的while循环结构\n”;

$left = 0;

$right = 9;

$step = 1;

while ($left <= $right) {

    $mid = (int)(($left + $right) / 2);

    echo “步骤 $step: left=$left, right=$right, mid=$mid\n”;

    // 模拟查找逻辑

    if ($mid == 5) {

        echo “找到目标位置: $mid\n”;

        break;

    } elseif ($mid > 5) {

        echo “mid > 目标，调整右边界\n”;

        $right = $mid – 1;

    } else {

        echo “mid < 目标，调整左边界\n”;

        $left = $mid + 1;

    }

    $step++;

}

echo “\n”;

//=================================================

// 示例8: do-while循环对比

echo “示例8: do-while循环 (至少执行一次)\n”;

$count = 10; // 初始条件就不满足

while ($count < 5) { // 这个循环不会执行

    echo “while循环: $count\n”;

    $count++;

}

$count = 10; // 初始条件同样不满足

do {

    echo “do-while循环: $count\n”; // 但do-while至少执行一次

    $count++;

} while ($count < 5);

echo “\n”;

//=================================================

// 示例9: 无限循环与break

echo “示例9: 使用break控制的循环\n”;

$counter = 0;

while (true) { // 看似无限循环

    $counter++;

    echo “循环次数: $counter\n”;

    if ($counter >= 3) {

        echo “达到条件，使用break退出循环\n”;

        break; // 跳出循环

    }

}

echo “\n”;

//=================================================

// 示例10: continue的使用

echo “示例10: 使用continue跳过某些迭代\n”;

$j = 0;

while ($j < 10) {

    $j++;

    if ($j % 2 == 0) {

        echo “跳过偶数: $j\n”;

        continue; // 跳过本次循环的剩余部分

    }

    echo “处理奇数: $j\n”;

}

echo “\n========== while循环演示结束 ==========\n”;

?>