String comparison functions in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of strcmp with different cases

What is the output of this PHP code snippet?

PHP

<?php
$str1 = "Hello";
$str2 = "hello";
$result = strcmp($str1, $str2);
echo $result;
?>

A 0

B 1

C -32

D SyntaxError

💡 Hint

strcmp compares strings byte by byte and is case-sensitive.

The strcmp function compares two strings in a case-sensitive way. Since uppercase 'H' has a lower ASCII value (72) than lowercase 'h' (104), the result is 72 - 104 = -32.

❓ Predict Output

intermediate

Output of strcasecmp with different cases

What will this PHP code output?

PHP

<?php
$str1 = "World";
$str2 = "world";
$result = strcasecmp($str1, $str2);
echo $result;
?>

A 0

B -1

C Warning: Undefined function

D 1

💡 Hint

strcasecmp compares strings ignoring case differences.

The strcasecmp function compares two strings ignoring case. Since "World" and "world" differ only in case, the result is 0, meaning they are equal.

❓ Predict Output

advanced

Behavior of strncmp with partial string comparison

What is the output of this PHP code?

PHP

<?php
$str1 = "apple";
$str2 = "apples";
$result = strncmp($str1, $str2, 5);
echo $result;
?>

A -1

B 0

C 1

D Fatal error

💡 Hint

strncmp compares only the first n characters of two strings.

The strncmp function compares only the first 5 characters: "apple" and "apple" (from "apples"), which are identical, so the result is 0.

❓ Predict Output

advanced

Output of substr_compare with offset and length

What does this PHP code output?

PHP

<?php
$str1 = "abcabc";
$str2 = "xyzabc";
$result = substr_compare($str1, $str2, 3, 3);
echo $result;
?>

A Warning: Wrong parameters

B 0

C 23

D -23

💡 Hint

substr_compare compares substrings starting at offset for given length.

The substrings compared are from offset 3 with length 3: "abc" from $str1 and "abc" from $str2 (starting at position 3).

Comparing 'a' (ASCII 97) and 'a' (ASCII 97), the difference is 0.

🧠 Conceptual

expert

Which function is best for case-insensitive string comparison with offset?

You want to compare two strings ignoring case, starting at a specific position and for a specific length. Which PHP function should you use?

A strncasecmp

B strncmp

C substr_compare

D strcasecmp

💡 Hint

Look for a function that combines case-insensitive, length-limited, and offset-based comparison.

strncasecmp performs case-insensitive comparison up to a specified length (but starts from the beginning of strings). For offset, substr() can be used first. substr_compare supports offset/length but is case-sensitive unless the optional case-insensitivity flag is set. Among options, strncasecmp fits case-insensitive partial comparison best.