定义和用法
PHP extract() 函数从数组中把变量导入到当前的符号表中。
对于数组中的每个元素,键名用于变量名,键值用于变量值。
第二个参数 type 用于指定当某个变量已经存在,而数组中又有同名元素时,extract() 函数如何对待这样的冲突。
本函数返回成功设置的变量数目。
语法<p class="sycode"> <p class="sycode"> extract ( array , extract_rules , prefix) </p> </p><p> </p>
array | 必需。规定要使用的输入。 |
extract_rules | 可选。extract() 函数将检查每个键名是否为合法的变量名,同时也检查和符号表中的变量名是否冲突。 对非法、数字和冲突的键名的处理将根据此参数决定。可以是以下值之一: 可能的值: EXTR_OVERWRITE - 默认。如果有冲突,则覆盖已有的变量。 EXTR_SKIP - 如果有冲突,不覆盖已有的变量。(忽略数组中同名的元素) EXTR_PREFIX_SAME - 如果有冲突,在变量名前加上前缀 prefix。自 PHP 4.0.5 起,这也包括了对数字索引的处理。 EXTR_PREFIX_ALL - 给所有变量名加上前缀 prefix(第三个参数)。 EXTR_PREFIX_INVALID - 仅在非法或数字变量名前加上前缀 prefix。本标记是 PHP 4.0.5 新加的。 EXTR_IF_EXISTS - 仅在当前符号表中已有同名变量时,覆盖它们的值。其它的都不处理。可以用在已经定义了一组合法的变量,然后要从一个数组例如 $_REQUEST 中提取值覆盖这些变量的场合。本标记是 PHP 4.2.0 新加的。 EXTR_PREFIX_IF_EXISTS - 仅在当前符号表中已有同名变量时,建立附加了前缀的变量名,其它的都不处理。本标记是 PHP 4.2.0 新加的。 EXTR_REFS - 将变量作为引用提取。这有力地表明了导入的变量仍然引用了 var_array 参数的值。可以单独使用这个标志或者在 extract_type 中用 OR 与其它任何标志结合使用。本标记是 PHP 4.3.0 新加的。 |
prefix | 可选。请注意 prefix 仅在 extract_type 的值是 EXTR_PREFIX_SAME,EXTR_PREFIX_ALL,EXTR_PREFIX_INVALID 或 EXTR_PREFIX_IF_EXISTS 时需要。如果附加了前缀后的结果不是合法的变量名,将不会导入到符号表中。 前缀和数组键名之间会自动加上一个下划线。 |
例子 1
<p class="sycode"> <p class="sycode"> <? php $a = ' Original ' ; $my_array = array ( " a " => " Cat " , " b " => " Dog " , " c " => " Horse " ); extract ( $my_array ); echo " \ $a = $a ; \ $b = $b ; \ $c = $c " ; ?> </p> </p><p> </p>
输出:
<p class="sycode"> <p class="sycode"> $a = Cat; $b = Dog; $c = Horse </p> </p><p> </p>
例子 2
使用全部参数:
<p class="sycode"> <p class="sycode"> <? php $a = ' Original ' ; $my_array = array ( " a " => " Cat " , " b " => " Dog " , " c " => " Horse " ); extract ( $my_array , EXTR_PREFIX_SAME , ' dup ' ); echo " \ $a = $a ; \ $b = $b ; \ $c = $c ; \ $dup_a = $dup_a ; " ; ?> </p> </p><p> </p>
输出:
<p class="sycode"> <p class="sycode"> $a = Original; $b = Dog; $c = Horse; $dup_a = Cat; </p> </p><p> </p>

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