echo "My variable value is: " . $my_variable_name;
echo "My index value is: " . $my_array["my_index"];

$o = [];
$var = ["",0,null,1,2,3,$foo,$o['myIndex']];
array_walk($var,function($v){
if(!isset($v) || $v == false) {
echo "emptyn";
}
if(empty($v)) {
echo "emptyn";
}
});

//Initializing variable
$value = ""; //Initialization value; Examples
             //"" When you want to append stuff later
             //0  When you want to add numbers later
//isset()
$value = isset($_POST['value']) ? $_POST['value'] : '';
//empty()
$value = !empty($_POST['value']) ? $_POST['value'] : '';

set_error_handler('myHandlerForMinorErrors', E_NOTICE | E_STRICT)

error_reporting( error_reporting() & ~E_NOTICE )

//isset()
$value = isset($array['my_index']) ? $array['my_index'] : '';
//array_key_exists()
$value = array_key_exists('my_index', $array) ? $array['my_index'] : '';

list($a, $b) = array(0 => 'a');
//or
list($one, $two) = explode(',', 'test string');

// recommended solution
$user_name = $_SESSION['user_name'];
if (empty($user_name)) $user_name = '';

OR

// just define at the top of the script index.php
$user_name = '';
$user_name = $_SESSION['user_name'];

OR

$user_name = $_SESSION['user_name'];
if (!isset($user_name)) $user_name = '';

// not the best solution, but works
// in your php setting use, it helps hiding site wide notices
error_reporting(E_ALL ^ E_NOTICE);

function ifexists($varname)
{
  return(isset($$varname)?$varname:null);
}

<?=ifexists('name')?>

function ifexistsidx($var,$index)
{
  return(isset($var[$index])?$var[$index]:null);
}

<?=ifexistsidx($_REQUEST,'name')?>

$a=10;
if($a==5) { $user_location='Paris';} else { }
echo $user_location;

$a=10;
if($a==5) { $user_location='Paris';} else { $user_location='SOMETHING OR BLANK'; }
echo $user_location;

$value = filter_input(INPUT_POST, 'value');

if (!isset($_POST['value'])) {
    $value = null;
} elseif (is_array($_POST['value'])) {
    $value = false;
} else {
    $value = $_POST['value'];
}

$value = (string)filter_input(INPUT_POST, 'value');

// Echo whatever the hell this is
<?=$_POST['something']?>

// If this is set, echo a filtered version
<?=isset($_POST['something']) ? html($_POST['something']) : ''?>

$user_location = null;

$greeting = "Hello, ".exst($user_name, 'Visitor')." from ".exst($user_location);


/**
 * Function exst() - Checks if the variable has been set
 * (copy/paste it in any place of your code)
 *
 * If the variable is set and not empty returns the variable (no transformation)
 * If the variable is not set or empty, returns the $default value
 *
 * @param  mixed $var
 * @param  mixed $default
 *
 * @return mixed
 */

function exst( & $var, $default = "")
{
    $t = "";
    if ( !isset($var)  || !$var ) {
        if (isset($default) && $default != "") $t = $default;
    }
    else  {
        $t = $var;
    }
    if (is_string($t)) $t = trim($t);
    return $t;
}

<?php
error_reporting(E_ALL); // making sure all notices are on

function idxVal(&$var, $default = null) {
         return empty($var) ? $var = $default : $var;
  }

echo idxVal($arr['test']);         // returns null without any notice
echo idxVal($arr['hey ho'], 'yo'); // returns yo and assigns it to array index, nice

?>

; Common Values:
;   E_ALL (Show all errors, warnings and notices including coding standards.)
;   E_ALL & ~E_NOTICE  (Show all errors, except for notices)
;   E_ALL & ~E_NOTICE & ~E_STRICT  (Show all errors, except for notices and coding standards warnings.)
;   E_COMPILE_ERROR|E_RECOVERABLE_ERROR|E_ERROR|E_CORE_ERROR  (Show only errors)
; Default Value: E_ALL & ~E_NOTICE & ~E_STRICT & ~E_DEPRECATED
; Development Value: E_ALL
; Production Value: E_ALL & ~E_DEPRECATED & ~E_STRICT
; http://php.net/error-reporting
error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT

function foo()
{
    $my_variable_name = '';

    //....

    if ($my_variable_name) {
        // perform some logic
    }
}

// verbose way - generally better
if (isset($my_array['my_index'])) {
    echo "My index value is: " . $my_array['my_index'];
}

// non-verbose ternary example - I use this sometimes for small rules.
$my_index_val = isset($my_array['my_index'])?$my_array['my_index']:'(undefined)';
echo "My index value is: " . $my_index_val;

$my_array = array(
    'my_index' => ''
);

//...

$my_array['my_index'] = 'new string';

echo "My variable value is: " . (isset($my_variable_name)) ? $my_variable_name : '';
echo "My index value is: " . (isset($my_array["my_index"])) ? $my_array["my_index"] : '';

echo "My variable value is: " . (isset($my_variable_name) && !empty($my_variable_name)) ? $my_variable_name : '';
echo "My index value is: " . (isset($my_array["my_index"]) && !empty($my_array["my_index"])) ? $my_array["my_index"] : '';