String comparison functions in PHP - Step-by-Step Execution

Concept Flow - String comparison functions

Start

↓

Get two strings

↓

Choose comparison function

↓

Compare strings

↓

Return comparison result

↓

Use result to decide next step

↓

End

The program gets two strings, compares them using a chosen function, then returns and uses the result.

Execution Sample

PHP

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

Compares two strings 'apple' and 'banana' using strcmp and prints the result.

Execution Table

Step	Action	Input Strings	Function Called	Return Value	Meaning
1	Initialize strings	$str1 = 'apple', $str2 = 'banana'	N/A	N/A	Strings ready for comparison
2	Call strcmp	'apple', 'banana'	strcmp	-1	'apple' is less than 'banana'
3	Print result	N/A	N/A	-1	Output is -1 showing order
4	End	N/A	N/A	N/A	Program ends

💡 All steps completed, comparison result printed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
$str1	undefined	apple	apple	apple	apple
$str2	undefined	banana	banana	banana	banana
$result	undefined	undefined	-1	-1	-1

Key Moments - 3 Insights

Why does strcmp return -1 instead of true or false?

strcmp returns an integer: negative if first string is less, zero if equal, positive if greater. See execution_table step 2 where -1 means 'apple' is less than 'banana'.

What happens if strings are equal?

If strings are equal, strcmp returns 0. This is shown by the return value meaning in execution_table step 2.

Why not use == to compare strings?

Using == checks equality only, but strcmp gives order info (less, equal, greater). This helps in sorting or ordering decisions.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of $result after step 2?

A 0

B -1

C 1

D undefined

💡 Hint

Check the 'Return Value' column in execution_table row for step 2.

At which step does the program print the comparison result?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the 'Print result' action in execution_table.

If $str1 was 'banana' and $str2 was 'apple', what would strcmp return?

A 1

B 0

C -1

D undefined

💡 Hint

strcmp returns positive if first string is greater; see meaning column in execution_table step 2.

Concept Snapshot

PHP string comparison functions:
- strcmp(str1, str2): returns <0 if str1 < str2, 0 if equal, >0 if str1 > str2
- Useful for sorting or ordering strings
- Returns integer, not boolean
- Use === or == for equality only

Full Transcript

This example shows how PHP compares two strings using strcmp. First, two strings are set: 'apple' and 'banana'. Then strcmp is called with these strings. It returns -1 because 'apple' comes before 'banana' alphabetically. The program prints this result. strcmp returns an integer indicating order: negative means first string is less, zero means equal, positive means greater. This helps decide string order, unlike simple equality checks. The execution table tracks each step and variable values. Beginners often confuse strcmp's return values with true/false, but it actually returns an integer to show order. This is important for sorting or comparing strings beyond equality.