String length and counting in PHP - Step-by-Step Execution

Concept Flow - String length and counting

Start with a string

↓

Call strlen() function

↓

Count characters in string

↓

Return length as integer

↓

Use length for output or logic

↓

End

This flow shows how PHP counts the number of characters in a string using strlen(), then returns that count for use.

Execution Sample

PHP

<?php
$str = "Hello";
$len = strlen($str);
echo $len;
?>

This code counts the characters in "Hello" and prints the length.

Execution Table

Step	Action	Variable	Value	Output
1	Assign string to $str	$str	"Hello"
2	Call strlen() on $str	strlen($str)	5
3	Assign length to $len	$len	5
4	Print $len	$len	5	5
5	End of script	-	-	-

💡 Script ends after printing the length 5.

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
$str	undefined	"Hello"	"Hello"	"Hello"
$len	undefined	undefined	5	5

Key Moments - 2 Insights

Why does strlen("Hello") return 5 and not 4 or 6?

Because strlen counts every character including letters and spaces exactly once. In the execution_table step 2, strlen("Hello") counts 5 letters: H, e, l, l, o.

What if the string is empty? What does strlen return?

If the string is empty (""), strlen returns 0 because there are no characters. This would be shown in step 2 with strlen("") = 0.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of $len after step 3?

A undefined

B 5

C Hello

D 0

💡 Hint

Check the 'Variable' and 'Value' columns at step 3 in execution_table.

At which step is the string length printed to output?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look for the step where Output column shows '5' in execution_table.

If $str was "Hi!", what would strlen($str) return?

A 2

B 4

C 3

D 5

💡 Hint

Count the characters in "Hi!" as done in execution_table step 2.

Concept Snapshot

strlen(string) returns the number of characters in a string.
Assign string to a variable.
Call strlen() with the string variable.
Store the result in another variable.
Use or print the length as needed.

Full Transcript

This example shows how PHP counts the length of a string using strlen(). First, a string "Hello" is stored in $str. Then strlen($str) counts the characters and returns 5. This value is saved in $len. Finally, $len is printed, showing 5. The process counts each character exactly once. If the string was empty, strlen would return 0. This helps in many tasks like validation or loops.