Array key and value extraction in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get all the keys from the array.

PHP

<?php
$fruits = ['a' => 'Apple', 'b' => 'Banana', 'c' => 'Cherry'];
$keys = array_[1]($fruits);
print_r($keys);
?>

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

Avalues

Bflip

Ckeys

Dmerge

Attempts:

3 left

💡 Hint

Common Mistakes

Using array_values instead of array_keys.

Trying to use array_flip which swaps keys and values.

The array_keys function returns all the keys from an array.

2fill in blank

medium

Complete the code to get all the values from the array.

PHP

<?php
$colors = ['red' => '#FF0000', 'green' => '#00FF00', 'blue' => '#0000FF'];
$values = array_[1]($colors);
print_r($values);
?>

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

Avalues

Bflip

Ckeys

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using array_keys instead of array_values.

Using array_pop which removes the last element.

The array_values function returns all the values from an array.

3fill in blank

hard

Fix the error in the code to swap keys and values of the array.

PHP

<?php
$items = ['pen' => 'blue', 'book' => 'red', 'bag' => 'black'];
$flipped = array_[1]($items);
print_r($flipped);
?>

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

Aflip

Breverse

Ckeys

Dvalues

Attempts:

3 left

💡 Hint

Common Mistakes

Using array_keys or array_values which do not swap keys and values.

Using array_reverse which reverses the order but does not swap keys and values.

The array_flip function swaps the keys and values of an array.

4fill in blank

hard

Fill both blanks to create an array of keys and values from the original array.

PHP

<?php
$person = ['name' => 'Alice', 'age' => 30, 'city' => 'Paris'];
$keys = array_[1]($person);
$values = array_[2]($person);
print_r($keys);
print_r($values);
?>

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

Akeys

Bvalues

Cflip

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up keys and values functions.

Using array_flip which swaps keys and values instead of extracting them.

Use array_keys to get keys and array_values to get values.

5fill in blank

hard

Fill all three blanks to create a flipped array and then get its keys and values.

PHP

<?php
$colors = ['red' => '#FF0000', 'green' => '#00FF00', 'blue' => '#0000FF'];
$flipped = array_[1]($colors);
$flipped_keys = array_[2]($flipped);
$flipped_values = array_[3]($flipped);
print_r($flipped_keys);
print_r($flipped_values);
?>

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

Aflip

Bvalues

Ckeys

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using array_pop which removes elements instead of extracting keys or values.

Mixing up keys and values order.

First flip the array, then get keys and values from the flipped array.

Practice

1. Which PHP function is used to extract all the keys from an array?

easy

A. array_map()

B. array_values()

C. array_keys()

D. array_filter()

Solution

1. Step 1: Understand the function purpose

   array_keys() returns all keys from an array.

2. Step 2: Compare with other functions

   array_values() returns values, not keys; others do different tasks.

3. Final Answer:

   array_keys() -> Option C

4. Quick Check:

   Keys extraction = array_keys() [OK]

Hint: Keys come from array_keys(), values from array_values() [OK]

Common Mistakes:

• Confusing array_keys() with array_values()
• Using array_map() to get keys
• Trying to get keys with array_filter()

2. Which of the following is the correct syntax to get all values from an array $arr in PHP?

easy

A. array_values($arr);

B. array_keys($arr);

C. values_array($arr);

D. get_values($arr);

Solution

1. Step 1: Identify the correct function name

   The function to get values is array_values().

2. Step 2: Check syntax correctness

   Correct syntax is array_values($arr); with parentheses and variable inside.

3. Final Answer:

   array_values($arr); -> Option A

4. Quick Check:

   Values extraction = array_values() [OK]

Hint: Values come from array_values(), keys from array_keys() [OK]

Common Mistakes:

• Using array_keys() to get values
• Using non-existent functions like values_array()
• Missing parentheses in function call

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

$arr = ['a' => 1, 'b' => 2, 'c' => 3];
print_r(array_keys($arr));

medium

A. Array ( [0] => 1 [1] => 2 [2] => 3 )

B. Array ( [0] => 'a' [1] => 'b' [2] => 'c' )

C. Array ( [a] => 1 [b] => 2 [c] => 3 )

D. Array ( [0] => a [1] => b [2] => c )

Solution

1. Step 1: Understand array_keys() output

   It returns an indexed array of all keys from the input array.

2. Step 2: Analyze given array keys

   Keys are strings 'a', 'b', 'c', so output is an indexed array with these strings.

3. Final Answer:

   Array ( [0] => a [1] => b [2] => c ) -> Option D

4. Quick Check:

   array_keys(['a'=>1,...]) = ['a','b','c'] [OK]

Hint: array_keys() returns keys as indexed array [OK]

Common Mistakes:

• Confusing keys with values in output
• Expecting associative array output
• Including quotes in output keys

4. Identify the error in this PHP code snippet:

$arr = ['x' => 10, 'y' => 20];
$keys = array_values($arr);
print_r($keys);

medium

A. array_values() should be array_keys() to get keys

B. Missing semicolon after array declaration

C. print_r() cannot print arrays

D. Variable $keys is not defined

Solution

1. Step 1: Understand the goal

   The code tries to get keys but uses array_values() which returns values.

2. Step 2: Correct function usage

   To get keys, use array_keys() instead of array_values().

3. Final Answer:

   array_values() should be array_keys() to get keys -> Option A

4. Quick Check:

   Keys need array_keys(), not array_values() [OK]

Hint: Use array_keys() for keys, array_values() for values [OK]

Common Mistakes:

• Mixing up array_keys() and array_values()
• Assuming print_r() can't print arrays
• Ignoring correct variable definitions

5. Given the array $data = ['apple' => 3, 'banana' => 0, 'cherry' => 5, 'date' => 0];, which PHP code correctly extracts only the keys with non-zero values?

hard

A. $keys = array_keys($data);

B. $keys = array_keys(array_filter($data));

C. $keys = array_values(array_filter($data));

D. $keys = array_filter(array_keys($data));

Solution

1. Step 1: Filter array to keep non-zero values

   array_filter($data) removes entries with zero values.

2. Step 2: Extract keys from filtered array

   array_keys() gets keys from the filtered array, giving only keys with non-zero values.

3. Final Answer:

   $keys = array_keys(array_filter($data)); -> Option B

4. Quick Check:

   Filter then keys = array_keys(array_filter()) [OK]

Hint: Filter first, then get keys with array_keys(array_filter()) [OK]

Common Mistakes:

• Using array_values() instead of array_keys() after filtering
• Not filtering before extracting keys
• Filtering keys instead of values