Detailed explanation of PHP arrays, detailed explanation of arrays_PHP tutorial

Detailed explanation of PHP arrays, detailed explanation of arrays

As a C programmer, in the process of switching to PHP development, I had some confusion about PHP arrays, which are similar to C arrays There are also some differences. Let’s comprehensively analyze the differences and connections between PHP arrays and the corresponding data types in C.

Classification of arrays:

1. Numeric array: also called index array, that is, numbers (starting from 0) are used as array subscripts. Equivalent to vector in C.

2. Associative array: Use string as array subscript. Equivalent to map in C.

3. Multidimensional array: Each element in the array is also an array. Each element in its subarray can also be an array.

Array declaration:

1. Numeric array

<span>a、如下例子中，会自动分配数字ID键。  
</span><span>$names</span> = <span>array</span>("Peter","Joe","Lily"<span>);  
b、如下例子中，我们人工分配数字ID键。  
</span><span>$names</span>[0] = "Peter"<span>;  
</span><span>$names</span>[1] = "Joe"<span>;  
</span><span>$names</span>[2] = "Lily"<span>;  
可以在脚本中使用这些ID键：  
</span><?<span>php  
    </span><span>$names</span>[0] = "Peter"<span>;  
    </span><span>$names</span>[1] = "Joe"<span>;  
    </span><span>$names</span>[2] = "Lily"<span>;  
    </span><span>echo</span> <span>$names</span>[0]." and ".<span>$names</span>[1]." are ".<span>$names</span>[2]."'s neighbors"<span>;  
</span><span>/*</span><span> 何问起 hovertree.com </span><span>*/</span>
?>  

2. Associative array:

<span>例子1  
</span><span>$ages</span> = <span>array</span>("Peter"=>32, "Joe"=>30, "Lily"=>28<span>);  
例子2  
本例与例子1相同，只是另一种创建数组的方法。  
</span><span>$ages</span>["Peter"] = "32"<span>;  
</span><span>$ages</span>["Joe"] = "30"<span>;  
</span><span>$ages</span>["Lily"] = "28"<span>;  
在脚本中使用关联数组：  
</span><?<span>php  
    </span><span>$ages</span>["Peter"] = "32"<span>;  
    </span><span>$ages</span>["Joe"] = "30"<span>;  
    </span><span>$ages</span>["Lily"] = "28"<span>;  
    </span><span>echo</span> "Peter is ".<span>$ages</span>["Peter"]." years old."<span>;  
</span><span>/*</span><span> 何问起 hovertree.com </span><span>*/</span>
?><span>  
以上脚本输出：  
Peter is </span>32 years old. 

3. Multidimensional array:

<span>在本例中，我们创建了一个带有自动分配数字ID键的多维数组：  
</span><span>$families</span> = <span>array</span><span>  
{  
    </span>"Griffin"=><span>array</span><span>  
    {  
        </span>"Peter",  
        "Lois",  
        "Megan"<span>  
    }</span>,  
    "Quagmire"=><span>array</span><span>  
    {  
        </span>"Glenn"<span>  
    }</span>,  
    "Brown"=><span>array</span><span>  
    {  
        </span>"Cleveland",  
        "Loretta",  
        "Junior"<span>  
    }  
};  
</span><span>echo</span> "Is " . <span>$families</span>['Griffin'][2] . " a part of the Griffin family?"<span>;  
以上代码输出：  
Is Megan a part of the Griffin family</span>?  

Array traversal

1<span>、for循环遍历  
for循环只能遍历索引数组。  
</span><?<span>php  
    </span><span>$names</span> = <span>array</span>("Peter","Joe","Lily"<span>);  
    </span><span>for</span>(<span>$id</span>=0;<span>$id</span><<span>count</span>(<span>$names</span>);++<span>$id</span><span>)  
    {  
        </span><span>echo</span> <span>$names</span>[<span>$id</span><span>];  
    }  
</span>?>  
2<span>、foreach遍历  
即可以遍历索引数组，也可以遍历关联数组  
遍历索引数组  
</span><span>foreach</span>(array_expression <span>as</span> <span>$value</span><span>)  
{  
    循环体;  
}  
遍历关联数组  
</span><span>foreach</span>(array_expression <span>as</span> <span>$key</span>=><span>$value</span><span>)  
{  
    循环体;  
}  
  
A、一维数组遍历  
索引数组  
</span><?<span>php  
    </span><span>$contact</span> = <span>array</span>("李某","xx公司","abc@xx.com"<span>);  
    </span><span>foreach</span>(<span>$contact</span> <span>as</span> <span>$value</span><span>)  
    {  
        </span><span>echo</span> <span>$value</span><span>;  
    }  
</span>?>  
  
<?<span>php  
    </span><span>$contact</span> = <span>array</span>("姓名"=>"李某","公司"=>"xx公司","邮箱"=>"abc@xx.com"<span>);  
    </span><span>foreach</span>(<span>$contact</span> <span>as</span> <span>$key</span>=><span>$value</span><span>)  
    {  
        </span><span>echo</span> <span>$key</span>.":".<span>$value</span><span>;  
    }  
</span>?><span>  
  
B、多维数组遍历  
</span><?<span>php  
    </span><span>$wage</span> = <span>array</span><span>(  
        </span>"市场部"=<span>array</span><span>(  
            </span><span>array</span>(1,"李某","市场经理",8000),  
            <span>array</span>(2,"王某","市场专员",5000),  
            <span>array</span>(3,"刘某","市场专员",7000<span>)  
        )</span>,  
        "产品部"=<span>array</span><span>(  
            </span><span>array</span>(1,"李某","产品经理",9000),  
            <span>array</span>(2,"王某","产品专员",6000),  
            <span>array</span>(3,"刘某","产品专员",5000<span>)  
        )</span>,  
        "账务部"=<span>array</span><span>(  
            </span><span>array</span>(1,"李某","账务经理",7000),  
            <span>array</span>(2,"王某","账务专员",6000),  
            <span>array</span>(3,"刘某","账务专员",5000<span>)  
        )  
    );  
      
    </span><span>foreach</span>(<span>$wage</span> <span>as</span> <span>$section</span>=><span>$table</span><span>)  
    {  
        </span><span>echo</span> <span>$section</span>."部门人员如下"<span>;  
        </span><span>foreach</span>(<span>$table</span> <span>as</span> <span>$row</span><span>)  
        {  
            </span><span>foreach</span>(<span>$row</span> <span>as</span> <span>$value</span><span>)  
            {  
                </span><span>echo</span> <span>$value</span><span>;  
            }  
        }  
    }  </span><span>/*</span><span> 何问起 hovertree.com </span><span>*/</span>
?>  

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