Implode and join in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code using implode?

Look at the PHP code below. What will it print?

PHP

<?php
$array = ['apple', 'banana', 'cherry'];
echo implode('-', $array);
?>

A apple-banana-cherry

B apple,banana,cherry

C apple banana cherry

D applebanana cherry

💡 Hint

implode joins array elements with the string you give as the first argument.

The implode function joins array elements into a string using the first argument as separator. Here, '-' is used, so the output is 'apple-banana-cherry'.

❓ Predict Output

intermediate

What does this PHP code output when using join()?

Check the PHP code below. What will it print?

PHP

<?php
$fruits = ['pear', 'grape', 'melon'];
echo join(', ', $fruits);
?>

A pear grape melon

B pear, grape, melon

C pear,grape,melon

D pear-grape-melon

💡 Hint

join() is an alias of implode(), so it works the same way.

join() works like implode(). The separator ', ' is used, so the output is 'pear, grape, melon'.

❓ Predict Output

advanced

What is the output of implode with a numeric array and no separator?

What will this PHP code print?

PHP

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

A 1234

B 1 2 3 4

C 1,2,3,4

D Array

💡 Hint

If the separator is an empty string, elements join without spaces or commas.

implode with an empty string joins elements directly, so output is '1234'.

❓ Predict Output

advanced

What error or output does this code produce?

Consider this PHP code. What happens when you run it?

PHP

<?php
$items = ['a', 'b', 'c'];
echo implode($items);
?>

A abc

B a b c

C a,b,c

D Warning: implode(): Invalid arguments passed

💡 Hint

implode expects the separator first, then the array.

Calling implode with only one argument as an array causes a warning because the separator is missing.

🧠 Conceptual

expert

How many items are in the resulting string after implode?

Given this PHP code, how many characters will the output string have?

PHP

<?php
$words = ['hi', 'there', 'friend'];
$output = implode(' ', $words);
echo strlen($output);
?>

A 13

B 15

C 14

D 16

💡 Hint

Count letters plus spaces between words.

The words are 'hi' (2), 'there' (5), 'friend' (6). Spaces between words are 2. Total length = 2+1+5+1+6 = 14.