if statement - php if, and, or : multiple variables to check. Working, but getting variable not defined errors -

basically i'm trying check if variable exists, if so, run snippet regardless if others exist or not.

i'm using:

if ($a1 || $a2 || $a3 || $a4): $a = "success"; endif;

if $a4 exists, works , set's $a variable fine. however, i'm getting variable not defined error's before $a4.

a different variable set if $a0 variable doesn't exist (null):

if (!empty($a0) && $a1 || $a2 || $a3 || $a4) : $a-alt = "no0success"; endif;

this code working fine. however, it's giving me variable not defined error.

make use of isset function, try this

if( isset($variable) ){    // , so.... }else {    // define variable    $variable = 'foo'; }

Call