Common PHP Code Review Mistakes and How to Fix Them

After doing many code reviews, I often see repeated errors; here are ways to correct them.

1. Test if array is empty before looping

$items = [];
// ...
if (count($items) > 0) {
    foreach ($items as $item) {
        // process on $item ...
    }
}

Both foreach and array functions ( array_*) can handle empty arrays.

No need to test beforehand.

Reduces one level of indentation.

2. Wrap code in a single if statement

function foo(User $user) {
    if (!$user->isDisabled()) {
        // ...
        // long process
        // ...
    }
}

Use early return to reduce nesting:

function foo(User $user) {
    if ($user->isDisabled()) {
        return;
    }
    // ...
    // other code
    // ...
}

3. Repeated calls to isset

Instead of checking each variable separately, isset can accept multiple arguments.

$a = null;
$b = null;
$c = null;
// ...
if (!isset($a, $b, $c)) {
    throw new Exception("undefined variable");
}

// or
if (isset($a, $b, $c)) {
    // process with $a, $b and $c
}

For nested arrays:

if (isset($items['user'], $items['user']['id'])) {
    // process with $items['user']['id']
}

4. Using echo with sprintf

$name = "John Doe";
echo sprintf('Bonjour %s', $name);

Prefer printf for direct output:

$name = "John Doe";
printf('Bonjour %s', $name);

5. Checking for a key in an array

$items = [
    'one_key' => 'John',
    'search_key' => 'Jane',
];
if (in_array('search_key', array_keys($items))) {
    // process
}

Replace the in_array + array_keys pattern with array_key_exists or isset:

if (array_key_exists('search_key', $items)) {
    // process
}

// or
if (isset($items['search_key'])) {
    // process
}