if select option is null then $_post undefined index? code example
Example 1: javascript check if undefined or null
if( typeof myVar === 'undefined' || myVar === null ){
// myVar is undefined or null
}
Example 2: javascript check if undefined or null
// simple check do the job
if (myVar) {
// comes here either myVar is not null,
// or myVar is not undefined,
// or myVar is not '' (empty string).
}