Hello,在PHP里,我想获得某个变量的名字,如
<code>$name = 'xiaomin'; echo get_varible_name($name); \\ output 'name' </code>
我在这里看到一段代码
<code>function get_variable_name(&$var, $scope = NULL) { if (NULL == $scope) { $scope = $GLOBALS; } $tmp = $var; $var = "tmp_exists_" . mt_rand(); $name = array_search($var, $scope, TRUE); $var = $tmp; return $name; } </code>
其中的$var = "tmp_exists_" . mt_rand();
是什么意思?谁能解释下
回复内容:
Hello,在PHP里,我想获得某个变量的名字,如
<code>$name = 'xiaomin'; echo get_varible_name($name); \\ output 'name' </code>
我在这里看到一段代码
<code>function get_variable_name(&$var, $scope = NULL) { if (NULL == $scope) { $scope = $GLOBALS; } $tmp = $var; $var = "tmp_exists_" . mt_rand(); $name = array_search($var, $scope, TRUE); $var = $tmp; return $name; } </code>
其中的$var = "tmp_exists_" . mt_rand();
是什么意思?谁能解释下
题主仔细读鸟哥的原文就会发现这句话:
显然, 我们需要根据变量的值去查询这个表, 找到值等于要找值的变量, 但是, 这样做又有一个问题, 那就是, 可能会有多个变量的值相等啊?
我们测试一下:
1.注释掉题主疑惑的那句话:
<code>$test1 = 123; $test2 = 123; function get_variable_name(&$var, $scope = NULL) { if (NULL == $scope) { $scope = $GLOBALS; } $tmp = $var; $var = "tmp_exists_" . mt_rand(); // $name = array_search($var, $scope, TRUE); $var = $tmp; return $name; } echo get_variable_name($test1)."\n"; echo get_variable_name($test2); </code>
我们看下输出:
//无法区分
2.现在我们取消注释:
<code>$test1 = 123; $test2 = 123; function get_variable_name(&$var, $scope = NULL) { if (NULL == $scope) { $scope = $GLOBALS; } $tmp = $var; $var = "tmp_exists_" . mt_rand(); $name = array_search($var, $scope, TRUE); $var = $tmp; return $name; } echo get_variable_name($test1)."\n"; echo get_variable_name($test2); </code>
输出如下:
//区分成功
首先回答题主的问题,目的是修改需要查找变量的值使其在全局变量中唯一。然后说下我对这个函数的理解:
这个函数有几处地方需要注意的:
- 首先是参数
&$var
,这里用了引用,需要注意一下,作用在后头会说。 - 然后是使用了
$GLOBALS
超全局变量 - 就是题主说的更改了
$var
变量的值
$GLOBALS超全局变量是一个数组,负责存储页面上所有的变量的,这个函数的意思是通过使用array_search()函数在这个全局变量数组中搜索这个变量值,如果存在的话则返回其键名。为了防止有重复的值出现,函数则使用了 mt_rand() 函数更改了 $var
的值为一个唯一随机变量并在查询结束之后重新把原值赋上,如果没有这句话的话在有变量存在相同值的情况下就无法分辨。
传进来的第一个参数是指向某变量的引用,这样可以在方法内部操作外面传进来的变量。
紧接着开始操作, 给外面的变量,先赋值一个随机、又不重复的临时值,方便在作用域(默认 GLOBAL)里按照值去查找。
找到之后,再把这个变量的值赋回去。
方法的关键是 array_search 的用法, 以值去搜索(所以要给个不可能重复的值),搜到后返回键名(GLOBAL 作用域下的变量, 都存在于 $GLOBAL[$key] = $value 这个数组里)。
函数利用了PHP的变量的变量这个概念.

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