PHP Comments

A comment is a note inside code that PHP ignores. Comments help people read the code around them.

A line comment

The comment sits on its own line. The echo line below it still runs.

<?php
// Print a greeting
echo "Hello\n";

A hash comment

This comment also sits on its own line. Only the echo line prints.

<?php
# Say hello again
echo "Hello again\n";

A block comment around a statement

The block comment covers one whole statement. That statement does not run, so only the second line prints.

<?php
/* echo "Hidden line\n"; */
echo "Visible line\n";

Example

<?php
// Print the plan for today
echo "Plan for today\n";
echo "Write one program\n"; // The second line of the plan

Key points

Use // to start a line comment.
A line comment runs to the end of its line.
A hash sign also starts a line comment.
Use /* to start a block comment and */ to end it.
A block comment can hide a statement so it does not run.

In this example, a line comment sits above the first echo line. The first line prints Plan for today. A short comment sits after the second echo line, and that line prints Write one program.

Note

A comment is for readers, and it changes nothing in the output.

Try it Yourself

Edit the code, then press Run.

Running is simulated

<?php
// Print the plan for today
echo "Plan for today\n";
echo "Write one program\n"; // The second line of the plan

Exercise

Which pair starts and ends a block comment?

/* and */ // and // # and #