Indexed array creation in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an indexed array in PHP?

An indexed array in PHP is a list of values where each value is automatically assigned a numeric index starting from 0.

beginner

How do you create an indexed array with three fruits: apple, banana, and cherry?

You can create it like this:
$fruits = array('apple', 'banana', 'cherry');
or using the short syntax:
$fruits = ['apple', 'banana', 'cherry'];

beginner

What index does the first element of an indexed array have in PHP?

The first element of an indexed array always has the index 0.

beginner

How can you add a new element to the end of an existing indexed array?

You can add a new element by using the empty square brackets:
$fruits[] = 'orange';
This adds 'orange' at the next available numeric index.

beginner

What will be the output of print_r($fruits); if $fruits = ['apple', 'banana']; $fruits[] = 'cherry';?

The output will be:

Array
(
    [0] => apple
    [1] => banana
    [2] => cherry
)

Which of the following creates an indexed array with values 10, 20, 30 in PHP?

A $numbers = <10, 20, 30>;

B $numbers = {10, 20, 30};

C $numbers = [10, 20, 30];

D $numbers = (10, 20, 30);

In PHP, indexed arrays are created using square brackets [] or the array() function. Curly braces, parentheses, or angle brackets are not valid for array creation.

What is the index of the element 'banana' in $fruits = ['apple', 'banana', 'cherry'];?

A 1

B 0

C 2

D 3

'banana' is the second element, so its index is 1 because indexing starts at 0.

How do you add 'grape' to the end of the array $fruits = ['apple', 'banana'];?

A $fruits['grape'] = true;

B $fruits[] = 'grape';

C array_push($fruits, 'grape');

D Both C and D

You can add an element by using empty brackets or the array_push() function. Both methods add 'grape' to the end.

What will count($fruits); return if $fruits = ['apple', 'banana', 'cherry'];?

A 2

B 3

C 0

D Error

count() returns the number of elements in the array, which is 3 here.

Which syntax is NOT valid for creating an indexed array in PHP?

A $arr = {1, 2, 3};

B $arr = [1, 2, 3];

C $arr = array(1, 2, 3);

D $arr = [];

Curly braces {} are not used for array creation in PHP.

Explain how to create an indexed array in PHP and how the indexes are assigned.

Think about how you list items in order without naming the keys.

Describe two ways to add a new element to an existing indexed array in PHP.

One way uses brackets, the other is a built-in function.

Practice

1. Which of the following correctly creates an indexed array with three elements in PHP?

easy

A. $arr = ["apple", "banana", "cherry"];

B. $arr = {"apple", "banana", "cherry"};

C. $arr = ("apple", "banana", "cherry");

D. $arr = array:"apple", "banana", "cherry";

Solution

1. Step 1: Recognize PHP array syntax

   PHP indexed arrays can be created using square brackets [] or the array() function.

2. Step 2: Check each option's syntax

   $arr = ["apple", "banana", "cherry"]; uses [] with comma-separated values, which is correct. Options A, B, and C use invalid syntax for arrays.

3. Final Answer:

   $arr = ["apple", "banana", "cherry"]; -> Option A

4. Quick Check:

   Correct array syntax = $arr = ["apple", "banana", "cherry"]; [OK]

Hint: Use square brackets [] or array() to create indexed arrays [OK]

Common Mistakes:

• Using curly braces {} instead of []
• Using parentheses () without array()
• Incorrect use of colons or other symbols

2. Which of the following is the correct syntax to create an indexed array with the elements 10, 20, and 30 in PHP?

easy

A. $numbers = [10; 20; 30];

B. $numbers = array(10, 20, 30);

C. $numbers = (10, 20, 30);

D. $numbers = {10, 20, 30};

Solution

1. Step 1: Recall PHP array creation syntax

   PHP allows creating arrays using array() with parentheses and comma-separated values.

2. Step 2: Validate each option

   $numbers = array(10, 20, 30); uses array() correctly. Options B, C, and D use invalid separators or brackets.

3. Final Answer:

   $numbers = array(10, 20, 30); -> Option B

4. Quick Check:

   array() with commas = $numbers = array(10, 20, 30); [OK]

Hint: Use commas inside array() or [] to separate elements [OK]

Common Mistakes:

• Using semicolons instead of commas
• Using parentheses without array()
• Using curly braces for arrays

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

$fruits = ["apple", "banana", "cherry"];
echo $fruits[1];

medium

A. banana

B. apple

C. cherry

D. Error

Solution

1. Step 1: Understand array indexing

   Indexed arrays start at index 0, so $fruits[0] = "apple", $fruits[1] = "banana".

2. Step 2: Identify the echoed element

   The code echoes $fruits[1], which is "banana".

3. Final Answer:

   banana -> Option A

4. Quick Check:

   Index 1 element = banana [OK]

Hint: Remember PHP arrays start at index 0 [OK]

Common Mistakes:

• Confusing index 1 with index 0
• Expecting output of entire array
• Syntax errors from missing semicolons

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

$colors = array["red", "green", "blue"];

medium

A. Array elements must be integers

B. Missing semicolon at the end

C. Using double quotes instead of single quotes

D. Using square brackets [] instead of parentheses () with array

Solution

1. Step 1: Check array() function syntax

   The array() function requires parentheses (), not square brackets [].

2. Step 2: Identify the syntax error

   The code uses array[ ... ] which is invalid syntax and causes an error.

3. Final Answer:

   Using square brackets [] instead of parentheses () with array -> Option D

4. Quick Check:

   array() needs () not [] [OK]

Hint: Use parentheses () with array(), not square brackets [] [OK]

Common Mistakes:

• Confusing array() with [] syntax
• Forgetting semicolon (though present here)
• Thinking quotes type matters for array creation

5. You want to create an indexed array of numbers from 1 to 5 in PHP without manually listing each number. Which code correctly does this?

hard

A. $numbers = array(1 to 5);

B. $numbers = [1..5];

C. $numbers = range(1, 5);

D. $numbers = {1, 2, 3, 4, 5};

Solution

1. Step 1: Recall PHP function for range creation

   PHP provides the range() function to create arrays with sequences of numbers.

2. Step 2: Evaluate each option

   $numbers = range(1, 5); uses range(1, 5) correctly. Options A, B, and D use invalid syntax or unsupported constructs.

3. Final Answer:

   $numbers = range(1, 5); -> Option C

4. Quick Check:

   Use range() for sequences [OK]

Hint: Use range(start, end) to create number arrays quickly [OK]

Common Mistakes:

• Using invalid range syntax like [1..5]
• Trying to write '1 to 5' inside array()
• Using curly braces {} for arrays