If statement with multiple logical comparison - php

Question

I need to check if $_POST['a'] is not empty AND is either '1' OR '2' so user cannot remove the a= or change the value from 1 or 2 to something else from the post path:
<?php
if(empty($_POST['a']) || !in_array($_POST['a'], array('1', '2'))) {
echo 'error1';
} else if ($_POST['a'] == '1') {
do something;
} else if ($_POST['a'] == '2') {
do something;
} else {
echo 'error2';
}
?>
Can anyone teach me how to do this in a correct way?
Many many thanks

Answer 1

You can use a switch instead:
switch ($_POST['a']):
case '':
// empty
echo 'error1';
break;
case '1':
// do something for 1
break;
case '2':
// do something for 2
break;
default:
// not empty but not 1 or 2
echo 'error2';
endswitch;

Answer 2

if (!empty($_POST['a']) && $_POST['a'] == '1') { //Not empty AND is 1
do something;
} else if (!empty($_POST['a']) && $_POST['a'] == '2') { //Not Empty AND is 2
do something;
} else {
echo 'error';
}
The first two will catch all "good" values, everything else will get the error. And no need for the top if in this case.

Answer 3

UPDATE: You have a syntax error. Missing a ) at the end of the first if.
Two easy ways of doing this:
// first condition should be by itself as it's a terminal error
if(empty($_POST['a']) or !in_array($_POST['a'], array('1', '2'))) {
echo 'error1';
die; // or redirect here or just enfore a default on $_POST['a'] = 1; // let's say
}
// Second can be like this or embraced in the else of the first one (se ex.2)
if ($_POST['a'] == '1') {
// do something;
} else if ($_POST['a'] == '2') {
// do something;
}
or
// first condition should be by itself as it's a terminal error
if(empty($_POST['a']) or !in_array($_POST['a'], array('1', '2'))) {
echo 'error1';
// or redirect here or just enfore a default on $_POST['a'] = 1; // let's say
}else{ // Second is in the else here :)
if ($_POST['a'] == '1') {
// do something;
} else if ($_POST['a'] == '2') {
// do something;
}
}
Your last else will not be reached as it will always end in the first if where you handle both emptiness and illegal value.