else if(PlayerData[playerid][Member] == 1)
{
 code
 return 1;
}
or
else if(PlayerData[playerid][Member] == 1)
{
 code
 without retrun 1;
}

// a is 10.
// b is 0 but it will change in the statements below.
new
    a = 10,
    b
;

if( a == 0 ) // if a is 0...
{
    b = 1; // ... set b to 1.
}
else if( a = 5 ) // if the above "if( a == 0 )" return false, that a is not 0, the next "else if" will be called. If a is 5...
{
    b = 2; // ... set b to 2.
}
else if( a = 10 ) // if the above is false, a is not 5, then this "else if" will be called. Is a equal to 10? Yes, it is!
{
    b = 3; // ... so set b to 3 and don't execute the rest of "else if" and/or "else" statements.
}
else
{
    b = 4;
}