How to get the name of a variable in php, how to get the variable in php_PHP tutorial

php method to get the name of a variable, php method to get the variable

In PHP, all variables are stored in the HastTable structure of the "symbol table", and the scope of the symbol is associated with the active symbol table. Therefore, there is only one active symbol table at a time.

We can get the current active symbol table through the get_defined_vars method.

get_defined_vars // Returns an array of all defined variables

Find the variable name based on its value, but be aware that variables with the same value may exist.

So first save the value of the current variable to a temporary variable, and then assign a unique value to the original variable to find the name of the variable. After finding the name, reassign the value of the temporary variable to the original variable.

Example 1:

<&#63;php 

$a = '100'; 

echo '$a name is:'.get_variable_name($a).' value:'.$a; // $a name is: a value: 100 

/** 
* @param String $var 要查找的变量 
* @param Array $scope 要搜寻的范围 
* @param String 变量名称 
*/ 
function get_variable_name(&$var, $scope=null){ 

$scope = $scope==null&#63; $GLOBALS : $scope; // 如果没有范围则在globals中找寻 

// 因有可能有相同值的变量,因此先将当前变量的值保存到一个临时变量中,然后再对原变量赋唯一值,以便查找出变量的名称,找到名字后,将临时变量的值重新赋值到原变量 
$tmp = $var; 

$var = 'tmp_value_'.mt_rand(); 
$name = array_search($var, $scope, true); // 根据值查找变量名称 

$var = $tmp; 
return $name; 
}
&#63;>

Example 2: Get the variable name defined in function

<&#63;php 
function test(){ 
$a = '100'; 
echo '$a name is:'.get_variable_name($a); 
} 

test(); // $a name is: undefined 
//因为在function中定义的变量globals会找不到 

function test2(){ 
$a = '100'; 
echo '$a name is:'.get_variable_name($a, get_defined_vars()); 
} 

test2(); // $a name is: a 
// 将scope设定为 get_defined_vars() 可以找到 

&#63;>

function vname(&$var, $scope=false, $prefix='unique', $suffix='value')
{
if($scope) $vals = $scope;
else $vals = $GLOBALS;
$old = $var;
$var = $new = $prefix.rand().$suffix;
$vname = FALSE;
foreach($vals as $key => $val) {
if($val === $new) $vname = $key;
}
$var = $old;
return $vname;
}

echo "\$variable name=".vname($variable name);
?>

Output result: $variable name =Variable name

1. The method above include("A.php") or require("A.php")
2. Attach the variable after passing the url, and use $_GET['variable name in B.php '] Get
3. Be more ruthless: set this variable to session or cookie