Originally published on zero2php.dev — part of the Zero to PHP course. View this lesson on the original site.

Single vs double quotes

Single quotes '...' are mostly literal; double quotes "..." can interpolate variables.

Example

<?php

declare(strict_types=1);

$name = 'Ada';
echo 'Hello $name', "\n";   // literal $name
echo "Hello $name", "\n";   // interpolates

Concatenation

Concatenate with .:

$greeting = 'Hello ' . $name . "\n";

Escapes

Escape sequences like "\n" and "\t" work in double-quoted strings; in single quotes, \ and ' are the common escapes.

Exercise

Set $name to Ada, then echo a double-quoted string so the output is exactly Hi Ada (one space after Hi).

From Zero to PHP — PHP foundations: environment, syntax, and values