PHP用foreach遍曆數組比較高效_PHP教程

foreach()有兩種用法：

foreach(array_name as $value)    {       statement;    }

這裡的array_name是你要遍曆的數組名，每次迴圈中，array_name數組的當前元素的值被賦給$value,並且數組內部的下標向下移一 步，也就是下次迴圈回得到下一個元素。

foreach(array_name as $key => $value)    {        statement;      } 

這裡跟第一種方法的區別就是多了個$key,也就是除了把當前元素的值賦給$value外，當前元素的索引值也會在每次迴圈中被賦給變數$key。索引值可以 是下標值，也可以是字串。比如book[0]=1中的"0"，book[id]="001"中的"id".

程式執行個體：

1

';$a = array(1, 2, 3, 17);foreach ($a as $v) {   echo "Current value of ".$a.":". $v."
";}?>// 運行結果foreach example 1: value only Current value of $a: 1Current value of $a: 2Current value of $a: 3Current value of $a: 17

2

/*-------------------------------------------------------------------------*//* foreach example 2: value (with key printed for illustration) */echo '
'.'
'."foreach example 2: value (with key printed for illustration) ".'
';$a = array(1, 2, 3, 17);$i = 0; /* for illustrative purposes only */foreach ($a as $v) {    echo ""$a[$i] => $v".'
';    $i++;}// 程式運行結果foreach example 2: value (with key printed for illustration) $a[0] => 1$a[1] => 2$a[2] => 3$a[3] => 17

3

/*-------------------------------------------------------------------------*//* foreach example 3: key and value */echo '
'.'
'."foreach example 3: key and value ".'
';$a = array(    "one" => 1,    "two" => 2,    "three" => 3,    "seventeen" => 17);foreach ($a as $k => $v) {    echo ""$a[$k] => $v".'
';}// 程式運行結果foreach example 3: key and value $a[one] => 1$a[two] => 2$a[three] => 3$a[seventeen] => 17

4

/*-------------------------------------------------------------------------*//* foreach example 4: multi-dimensional arrays */echo '
'.'
'."foreach example 4: multi-dimensional arrays ".'
';$a = array();$a[0][0] = "a";$a[0][1] = "b";$a[1][0] = "y";$a[1][1] = "z";foreach ($a as $v1) {    foreach ($v1 as $v2) {        echo "$v2"n";    }}// 程式運行結果foreach example 4: multi-dimensional arrays a b y z

5

/*-------------------------------------------------------------------------*//* foreach example 5: dynamic arrays */echo '
'.'
'."foreach example 5: dynamic arrays ".'
';foreach (array(1, 2, 3, 4, 5) as $v) {    echo "$v"n";}// 程式運行結果foreach example 5: dynamic arrays 1 2 3 4 5

也可以這麼用：

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