For Loop
Part of the Fundamentals section of Coddy's PHP journey — lesson 47 of 71.
Loops allow you to execute a block of code multiple times without writing it repeatedly. The for loop is ideal when you know exactly how many times you want to repeat something.
A for loop has three parts separated by semicolons: initialization, condition, and increment.
<?php
for ($i = 1; $i <= 5; $i++) {
echo $i . "\n";
}
?>This outputs the numbers 1 through 5, each on a new line. Here's how it works:
$i = 1— sets the starting value (runs once)$i <= 5— checks if the loop should continue$i++— increases$iafter each iteration
The loop keeps running as long as the condition is true. Once $i becomes 6, the condition fails and the loop stops.
You can also count backwards or use different step values:
<?php
for ($i = 10; $i >= 0; $i -= 2) {
echo $i . "\n";
}
?>This counts down from 10 to 0 by twos: 10, 8, 6, 4, 2, 0.
Challenge
EasyRead two integers from input: a starting number and an ending number.
Use a for loop to print all numbers from the starting number to the ending number (inclusive), each on a separate line.
Example 1:
If the inputs are 3 and 7, the output should be:
3
4
5
6
7Example 2:
If the inputs are 1 and 4, the output should be:
1
2
3
4Cheat sheet
The for loop executes a block of code a specific number of times. It has three parts separated by semicolons: initialization, condition, and increment.
<?php
for ($i = 1; $i <= 5; $i++) {
echo $i . "\n";
}
?>How it works:
$i = 1— initialization: sets the starting value (runs once)$i <= 5— condition: checks if the loop should continue$i++— increment: increases$iafter each iteration
The loop continues as long as the condition is true.
You can count backwards or use different step values:
<?php
for ($i = 10; $i >= 0; $i -= 2) {
echo $i . "\n";
}
?>Try it yourself
<?php
// Read input
$start = intval(fgets(STDIN));
$end = intval(fgets(STDIN));
// TODO: Write your code below using a for loop to print numbers from start to end
?>
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Fundamentals
4Comparison & Logical Operators
Comparison OperatorsEquality & IdentityLogical Operators Part 1Logical Operators Part 2Recap - Simple Logic2Variables and Data Types
NumbersStrings and QuotesBooleansNaming ConventionsRecap - Variable InitEmpty VariablesString ConcatenationGetting User InputCast to Different Types5Conditional Logic
If StatementIf - ElseThe Ternary OperatorNull Coalescing OperatorSwitch StatementRecap - Making Decisions3Basic Operators
Arithmetic OperatorsModulo OperatorExponentiation OperatorCombined AssignmentIncrement/DecrementOperator PrecedenceRecap - Simple CalculationsString Operators