Array count and length in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to count the number of elements in the array.

PHP

<?php
$fruits = ['apple', 'banana', 'cherry'];
$count = [1]($fruits);
echo $count;
?>

Drag options to blanks, or click blank then click option'

Acount

Blength

Csize

Dtotal

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'length' which is not a PHP function for arrays.

Using 'size' or 'total' which do not exist as PHP functions.

The count() function returns the number of elements in an array.

2fill in blank

medium

Complete the code to get the length of the string stored in the array element.

PHP

<?php
$words = ['hello', 'world'];
$length = [1]($words[0]);
echo $length;
?>

Drag options to blanks, or click blank then click option'

Astrlen

Blength

Csize

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'count' which counts array elements, not string length.

Using 'size' or 'length' which are not PHP functions.

The strlen() function returns the length of a string in PHP.

3fill in blank

hard

Fix the error in the code to correctly count the elements in the array.

PHP

<?php
$numbers = [1, 2, 3, 4];
$total = [1]($numbers);
echo $total;
?>

Drag options to blanks, or click blank then click option'

Asize

Bcount

Cstrlen

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() which is not a PHP function.

Using strlen() on arrays causes errors.

The correct function to count array elements is count(). Using length or strlen causes errors.

4fill in blank

hard

Fill both blanks to create an associative array with word lengths for words longer than 3 characters.

PHP

<?php
$words = ['cat', 'house', 'dog', 'elephant'];
$lengths = [];
foreach($words as [1]) {
  if(strlen([1]) > 3) {
    $lengths[[1]] = [2];
  }
}
print_r($lengths);
?>

Drag options to blanks, or click blank then click option'

A$word

Bstrlen('word')

C'length'

Dstrlen($word)

Attempts:

3 left

💡 Hint

Common Mistakes

Using string literals instead of variables for keys.

Using strlen('word') which returns length of the literal 'word', not the variable.

In PHP, to create an associative array with keys and values, you use the syntax 'key' => value. Here, the key is the word itself, and the value is its length using strlen($word).

5fill in blank

hard

Fill all three blanks to create a filtered array of words longer than 4 characters with their lengths.

PHP

<?php
$words = ['sun', 'moon', 'stars', 'sky'];
$result = array_filter(array_map(function([1]) {
    return ['[2]' => [1], '[3]' => strlen([1])];
}, $words), function($item) {
    return $item['length'] > 4;
});
print_r($result);
?>

Drag options to blanks, or click blank then click option'

A$word

Bword

Clength

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names without $ in function parameters.

Using incorrect keys like 'name' instead of 'word' or 'length'.

The function parameter should be $word. The key for the word is 'word' and the key for length is 'length'. This creates an array of words with their lengths, then filters those longer than 4.

Practice

1. What does the PHP function count() do when used on an array?

easy

A. It returns the number of elements in the array.

B. It returns the sum of all elements in the array.

C. It returns the last element of the array.

D. It sorts the array in ascending order.

Solution

1. Step 1: Understand the purpose of count()

   The count() function in PHP is designed to return how many items are inside an array.

2. Step 2: Compare with other options

   The other options describe summing elements, returning the last element, or sorting the array, which are unrelated to counting elements.

3. Final Answer:

   It returns the number of elements in the array. -> Option A

4. Quick Check:

   count() = number of elements [OK]

Hint: Remember: count() tells how many items, not their values. [OK]

Common Mistakes:

• Thinking count() sums values instead of counting items
• Confusing count() with functions that return elements
• Assuming count() sorts or changes the array

2. Which of the following is the correct syntax to get the number of elements in an array $arr in PHP?

easy

A. length($arr);

B. sizeofArray($arr);

C. size($arr);

D. count($arr);

Solution

1. Step 1: Recall PHP function for array length

   PHP uses count() to get the number of elements in an array.

2. Step 2: Check other options for validity

   Functions like length(), size(), or sizeofArray() do not exist or are incorrect in PHP.

3. Final Answer:

   count($arr); -> Option D

4. Quick Check:

   Use count() for array size [OK]

Hint: Use count() to get array size, not length() or size(). [OK]

Common Mistakes:

• Using length() which is not a PHP function
• Confusing count() with size() or sizeofArray()
• Adding semicolon inside function parentheses

3. What will be the output of the following PHP code?

$fruits = ['apple', 'banana', 'cherry'];
echo count($fruits);

medium

A. 0

B. 3

C. applebanana cherry

D. Error

Solution

1. Step 1: Identify the array elements

   The array $fruits contains three elements: 'apple', 'banana', and 'cherry'.

2. Step 2: Apply count() function

   The count() function returns the number of elements, which is 3.

3. Final Answer:

   3 -> Option B

4. Quick Check:

   count(['apple','banana','cherry']) = 3 [OK]

Hint: Count returns number of items, not their values. [OK]

Common Mistakes:

• Expecting count() to print array contents
• Confusing count() with string concatenation
• Thinking count() returns 0 for non-empty arrays

4. Consider this PHP code snippet:

$numbers = [1, 2, 3, 4];
$count = count($numbers
echo $count;

What is the problem with this code?

medium

A. Missing semicolon after count() function call.

B. count() cannot be used on numeric arrays.

C. Missing closing parenthesis in count() function call.

D. Variable $count is not defined before use.

Solution

1. Step 1: Check syntax of count() call

   The code count($numbers is missing a closing parenthesis ")".

2. Step 2: Verify other syntax elements

   There is no semicolon after the count() call, but the bigger issue is the missing parenthesis which causes a syntax error first.

3. Final Answer:

   Missing closing parenthesis in count() function call. -> Option C

4. Quick Check:

   count() needs matching parentheses [OK]

Hint: Always check parentheses balance in function calls. [OK]

Common Mistakes:

• Ignoring missing parenthesis and blaming semicolon
• Thinking count() can't be used on numeric arrays
• Assuming variable must be declared before assignment

5. You have an associative array in PHP:

$person = ['name' => 'Alice', 'age' => 30, 'city' => 'Paris'];

Which code correctly checks if the array has exactly 3 elements before printing "Valid"?

hard

A. if (count($person) == 3) { echo "Valid"; }

B. if (sizeof($person) > 3) { echo "Valid"; }

C. if (count($person) < 3) { echo "Valid"; }

D. if (length($person) == 3) { echo "Valid"; }

Solution

1. Step 1: Understand the array and count() usage

   The array $person has 3 key-value pairs. Using count() returns the number of elements.

2. Step 2: Check the condition for exactly 3 elements

   if (count($person) == 3) { echo "Valid"; } correctly uses count($person) == 3 to check if the array has exactly 3 elements.

3. Final Answer:

   if (count($person) == 3) { echo "Valid"; } -> Option A

4. Quick Check:

   count() == 3 means array has 3 elements [OK]

Hint: Use count() == number to check exact array size. [OK]

Common Mistakes:

• Using sizeof() with wrong comparison operator
• Using length() which is not a PHP function
• Checking for less or greater instead of exact count