Returning array inside function that returns another value

Question

Why does the following script does not work?

$arr = array();

function collect( $array , $val) {
    $array[] = $val;
    return $array;
}

function checkFoo( $s ) {

    $valid = true;

    if ( strlen( $s ) === 0 ) {
        $isValid = false;
        collectFoo( $arr , $s );
    }

    return $valid;
}

function checkBar( $t ) {

    $valid = true;

    if ( strlen( $s ) != 10 ) {
        $isValid = false;
        collectFoo( $arr , $t );
    }

    return $valid;
}

if ( checkFoo( $that ) && checkBar( $this ) ) {

    echo "success"; 

} else {

    print_r( $error );

}

I always get

Notice: Undefined variable: error in /my.php on line 12

where line 12 resembles the second occurrence of collect(...);

I know that a function can only return one value, but what if a function returns something in a function that returns something? Because collect returns $array inside checkBar that returns $valid.

what is `$this` and `$that` and `$error` and `collectFoo` function ? — DJafari, Feb 15 '13 at 22:52
`$this` & `$that` are placeholders. `$error` is an array that is just still there from debugging, `collectFoo` is a function that adds something to an array. — Sven, Feb 15 '13 at 23:08

score 1 · Accepted Answer · answered Feb 15 '13 at 22:49

you are using a global variable ($arr), so you need do declare it as such. example:

function checkFoo( $s ) {
    global $arr; // declare $arr to be usable inside this function scope
    $valid = true;

    if ( strlen( $s ) === 0 ) {
        $isValid = false;
        collectFoo( $arr , $s );
    }

    return $valid;
}

DJafari · Answer 2 · 2013-02-15T23:11:32.977

Edited

You need more practice, because totally your code is incorrect ! you must changes this parts of your codes :

$arr = array();

function collectFoo( $arr , $val) {
    global $arr;

    $arr[] = $val;
}

function checkFoo( $s ) {
    global $arr;

    $valid = false;
    if ( strlen( $s ) === 0 ) {
        $valid = false;
        collectFoo( $arr , $s );
    }
    return $valid;
}

function checkBar( $t ) {
    global $arr;

    $valid = true;
    if ( strlen( $t ) != 10 ) {
        $valid = false;
        collectFoo( $arr , $t );
    }
    return $valid;
}

$a = checkFoo( $that );
$b = checkBar( $this );
if ( $a && $b ) {
    echo 'Success !';
} else {
    print_r( $err );
}

Sorry, but I only get `Array ( [0] => [1] => )` – Sven Feb 15 '13 at 23:19 — Sven, Feb 15 '13 at 23:19

score 0 · Answer 3 · edited May 23 '17 at 12:27

You aren't declaring your $arr variable as global inside the functions that use it. You can find some info about that here.

Also, it doesn't look like you are actually using the return value of collect, so I'd say that your problem is that either checkBar or checkFoo are returning false, which makes you fall through to the print_r function, with a $error variable that you have not initialized.

Finally, it seems to me like your collect function is not actually doing anything to the $arr variable, because you are not passing it to collect by reference. you can read up on passing variables by reference here. There is also a S.O. question about this here.

Returning array inside function that returns another value

3 Answers3