How to get a variable name as a string in PHP?
In this tutorial, we’re going to see how to get the name of a variable by accessing get_defined_vars().
There is no predefined function in PHP that can output the name of a variable. However, you can use the result of get_defined_vars(), which returns all the variables defined in the scope, including name and value.
Definition of your own function
<?php
// Function for determining the name of a variable
function getVarName(&$var, $definedVars=null) {
$definedVars = (!is_array($definedVars) ? $GLOBALS : $definedVars);
$val = $var;
$rand = 1;
while (in_array($rand, $definedVars, true)) {
$rand = md5(mt_rand(10000, 1000000));
}
$var = $rand;
foreach ($definedVars as $dvName=>$dvVal) {
if ($dvVal === $rand) {
$var = $val;
return $dvName;
}
}
return null;
}
// the name of $a is to be determined.
$a = 1;
// Determine the name of $a
echo getVarName($a);
?>
Output:
a
The function getVarName() proceeds as follows:
- The variable for which the name is to be determined is received as a reference. This is important because the value must be adjusted below.
- The old value of the variable is saved.
- The value of the variable is temporarily changed to a random value that does not yet appear among the defined variables.
- The variable that has this random value is searched for among the defined variables.
- The value of this variable is reset to the saved value.
- The name of this variable is returned.
getVarName() in the scope of a function
In the previous example, the function was called in the global scope (top level). In this case, the result of get_defined_vars() does not have to be transferred, the function then automatically uses $GLOBALS. However, if you are in a function, then get_defined_vars() must be used once.
<?php
// insert the getVarName function from the previous example here
function myfunction()
{
$a = 1;
var_dump(getVarName($a)); // this call does not find $a
var_dump(getVarName($a, get_defined_vars())); // with this it will be found
}
myfunction();
?>
Output:
a
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