PHP Comments
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Single-Line Comments
A // or # comment tells PHP to ignore everything from that point to the end of the line. They're best for short, single-line notes — flagging a workaround, or reminding yourself why a value is hardcoded — rather than for explaining large blocks of logic.
Example: Single-Line Comments
<?php
// This is a single-line comment
# So is this
echo "Comments above are ignored";
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Multi-Line Comments
A /* ... */ comment can span multiple lines, making it the right tool for longer explanations: describing what a function does, documenting expected parameters, or temporarily annotating a tricky algorithm before you forget your own reasoning.
Example: Multi-Line Comments
<?php
/*
* This function doubles a number.
* Spans multiple lines to explain the logic.
*/
echo 5 * 2;
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Documenting Code
The most useful comments explain *why* a piece of code exists in a non-obvious form — a workaround for a browser quirk, a business rule that isn't visible from the code alone — rather than restating *what* the code does, which the code itself already shows.
Example: Documenting Code
<?php
// Workaround: legacy API returns price in cents, so we divide by 100
$price = 1999 / 100;
echo $price;
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Commenting Out Code
Wrapping a line (or block) in comment markers is a fast way to disable code temporarily while debugging, without deleting it outright. It's a normal part of the debugging workflow, but commented-out code left behind in a shipped file tends to rot and confuse the next reader.
Example: Commenting Out Code
<?php
echo "This line runs.\n";
// echo "This line is disabled while debugging.\n";
echo "This line also runs.\n";
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Comment Best Practices
Comments that don't match the code anymore are worse than no comment at all, because they actively mislead. Keep comments short, keep them focused on non-obvious intent, and update or delete them the moment the code they describe changes.
Example: Comment Best Practices
<?php
// Calculates the discounted price
function discount($price) {
return $price * 0.9;
}
echo discount(100);
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