Substring extraction in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP substring extraction?

Consider the following PHP code. What will it output?

PHP

<?php
$text = "Hello, world!";
echo substr($text, 7, 5);
?>

A world

B world!

C Hello

D o, wo

💡 Hint

Remember that substr starts at the offset and extracts the given length.

substr($text, 7, 5) starts at index 7 (0-based) and extracts 5 characters: 'world'.

❓ Predict Output

intermediate

What substring does this code extract?

What will be the output of this PHP code snippet?

PHP

<?php
$str = "Programming";
echo substr($str, -6, 3);
?>

A ram

B amm

C ogr

D ing

💡 Hint

Negative start means counting from the end of the string.

substr($str, -6, 3) starts 6 characters from the end and extracts 3 characters: 'amm'.

❓ Predict Output

advanced

What is the output when length exceeds string end?

What will this PHP code output?

PHP

<?php
$s = "OpenAI";
echo substr($s, 3, 10);
?>

A nAI

B nAI"

C enAI

D SyntaxError

💡 Hint

If length goes beyond string end, substr returns until the end.

substr($s, 3, 10) starts at index 3 and extracts till the end: 'nAI'.

❓ Predict Output

advanced

What happens if start is beyond string length?

What will this PHP code output?

PHP

<?php
$str = "Data";
echo substr($str, 10, 2);
?>

A ta

B Da

C Error: Out of bounds

D "" (empty string)

💡 Hint

If start is beyond string length, substr returns empty string.

substr($str, 10, 2) starts beyond string length, so returns empty string.

❓ Predict Output

expert

What is the output of this nested substring extraction?

Analyze the code and find the output:

PHP

<?php
$text = "abcdefg";
$part = substr($text, 2, 4);
echo substr($part, 1, 2);
?>

A cd

B bc

C de

D ef

💡 Hint

First extract 4 chars from index 2, then extract 2 chars from index 1 of that result.

substr($text, 2, 4) is 'cdef'. Then substr('cdef', 1, 2) is 'de'.