PHP

php get variable by string name

${$variableName} or $$variableName;

//example:

$variableName = 'foo';
$foo = 'bar';

// The following are all equivalent, and all output "bar":
echo $foo;
echo ${$variableName};
echo $$variableName;

php get variable name as a string

function print_var_name(){
    // read backtrace
    $bt   = debug_backtrace();
    // read file
    $file = file($bt[0]['file']);
    // select exact print_var_name($varname) line
    $src  = $file[$bt[0]['line']-1];
    // search pattern
    $pat = '#(.*)'.__FUNCTION__.' *?( *?(.*) *?)(.*)#i';
    // extract $varname from match no 2
    $var  = preg_replace($pat, '$2', $src);
    // print to browser
    echo trim($var);
}