Associative array creation in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an associative array with keys 'name' and 'age'.

PHP

$person = array('name' => 'John', 'age' => [1]);

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

AJohn

B'30'

C30

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Putting quotes around the number, making it a string.

Using a variable name instead of a value.

The value for the key 'age' should be a number without quotes to represent an integer.

2fill in blank

medium

Complete the code to add a new key 'city' with value 'Paris' to the associative array.

PHP

$person['city'] = [1];

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

A'Paris'

BParis

C"Paris"

Dcity

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the string value.

Using the key name as the value.

String values in PHP must be enclosed in quotes, either single or double.

3fill in blank

hard

Fix the error in the associative array creation by completing the code.

PHP

$data = array([1] => 'apple', 'b' => 'banana');

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

A'a'

Ba

C1

D"a"

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted strings as keys.

Using numbers when a string key is intended.

Keys in associative arrays must be strings or integers. Strings must be quoted.

4fill in blank

hard

Fill both blanks to create an associative array with keys 'x' and 'y' and values 10 and 20.

PHP

$coords = array([1] => [2], 'y' => 20);

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

A'x'

B10

C'10'

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted keys.

Putting quotes around numeric values.

The key 'x' must be a string with quotes, and the value 10 is a number without quotes.

5fill in blank

hard

Fill all three blanks to create an associative array with keys 'first', 'second', 'third' and values 1, 2, 3.

PHP

$numbers = array([1] => [2], [3] => 3);

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

A'first'

B1

C'second'

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting string keys.

Quoting numeric values.

Keys must be strings with quotes, and values are numbers without quotes.

Practice

1. Which of the following is the correct way to create an associative array in PHP with keys "name" and "age"?

easy

A. $person = ("name" => "Alice", "age" => 30);

B. $person = {"name": "Alice", "age": 30};

C. $person = array("Alice", 30);

D. $person = ["name" => "Alice", "age" => 30];

Solution

1. Step 1: Understand PHP associative array syntax

   Associative arrays use square brackets with key => value pairs.

2. Step 2: Identify correct syntax among options

   $person = ["name" => "Alice", "age" => 30]; uses square brackets and => correctly; others use invalid syntax.

3. Final Answer:

   $person = ["name" => "Alice", "age" => 30]; -> Option D

4. Quick Check:

   Associative array = key => value pairs [OK]

Hint: Use square brackets and => for associative arrays [OK]

Common Mistakes:

• Using parentheses instead of square brackets
• Using colon (:) instead of =>
• Creating indexed arrays instead of associative

2. Which of the following PHP code snippets will cause a syntax error when creating an associative array?

easy

A. $data = ["key1" : "value1", "key2" : "value2"];

B. $data = array("key1" => "value1", "key2" => "value2");

C. $data = ["key1" => "value1", "key2" => "value2"];

D. $data = ['key1' => 'value1', 'key2' => 'value2'];

Solution

1. Step 1: Check the syntax for key-value pairs

   PHP uses => to assign values to keys, not colon (:).

2. Step 2: Identify the invalid syntax

   $data = ["key1" : "value1", "key2" : "value2"]; uses colon (:) which is invalid in PHP associative arrays.

3. Final Answer:

   $data = ["key1" : "value1", "key2" : "value2"]; -> Option A

4. Quick Check:

   Use => not : for keys in PHP arrays [OK]

Hint: Remember PHP uses =>, not : for associative arrays [OK]

Common Mistakes:

• Using colon (:) instead of =>
• Mixing array() and [] syntax incorrectly
• Missing commas between pairs

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

$arr = ["fruit" => "apple", "color" => "red"];
echo $arr["color"];

medium

A. red

B. color

C. apple

D. fruit

Solution

1. Step 1: Understand array key access

   Accessing $arr["color"] returns the value for key "color".

2. Step 2: Identify the value for key "color"

   Value is "red", so echo outputs "red".

3. Final Answer:

   red -> Option A

4. Quick Check:

   Key "color" = "red" [OK]

Hint: Access values by keys with $array["key"] [OK]

Common Mistakes:

• Confusing keys and values
• Using wrong quotes or missing quotes
• Trying to access with dot notation

4. Identify the error in the following PHP code that tries to create an associative array:

$info = ["name" => "John", "age" = 25];

medium

A. Missing comma between elements

B. Keys should not be in quotes

C. Using = instead of => for key-value pair

D. Array must use array() syntax

Solution

1. Step 1: Check key-value assignment syntax

   PHP requires => to assign values to keys, not =.

2. Step 2: Locate incorrect assignment

   "age" = 25 uses = instead of =>, causing syntax error.

3. Final Answer:

   Using = instead of => for key-value pair -> Option C

4. Quick Check:

   Use => for key-value pairs [OK]

Hint: Use =>, not =, between key and value [OK]

Common Mistakes:

• Using single = instead of =>
• Omitting commas between pairs
• Not quoting string keys

5. You want to create an associative array in PHP that maps product names to their prices, but only include products with a price greater than 20. Which code correctly creates this filtered associative array?

hard

A. $products = ["apple" => 15, "banana" => 25, "cherry" => 30];
$filtered = [];
foreach ($products as $name, $price) {
if ($price > 20) {
$filtered[$name] = $price;
}
}

B. $products = ["apple" => 15, "banana" => 25, "cherry" => 30];
$filtered = [];
foreach ($products as $name => $price) {
if ($price > 20) {
$filtered[$name] = $price;
}
}

C. $products = ["apple" => 15, "banana" => 25, "cherry" => 30];
$filtered = array_filter($products, function($name, $price) {
return $price > 20;
});

D. $products = ["apple" => 15, "banana" => 25, "cherry" => 30];
$filtered = [];
foreach ($products as $price => $name) {
if ($price > 20) {
$filtered[$name] = $price;
}
}

Solution

1. Step 1: Understand foreach key-value syntax

   Use foreach ($array as $key => $value) to access keys and values correctly.

2. Step 2: Filter products with price > 20

   $products = ["apple" => 15, "banana" => 25, "cherry" => 30]; $filtered = []; foreach ($products as $name => $price) { if ($price > 20) { $filtered[$name] = $price; } } correctly checks price and assigns filtered items to new array.

3. Final Answer:

   The code using foreach ($products as $name => $price) -> Option B

4. Quick Check:

   foreach ($arr as $key => $value) for associative arrays [OK]

Hint: Use foreach ($arr as $key => $value) to access associative arrays [OK]

Common Mistakes:

• Swapping key and value variables in foreach
• Using incorrect foreach syntax with two variables separated by comma
• Misusing array_filter with wrong callback parameters