What are the differences between using single quotes and double quotes in PHP string concatenation?

When concatenating strings in PHP, the main difference between using single quotes and double quotes is that double quotes allow for variable interpolation, meaning that variables within the string will be evaluated and replaced with their values. Single quotes, on the other hand, treat everything within them as a literal string, so variables will not be evaluated and will appear as is. To concatenate strings with variables using double quotes, simply enclose the entire string within double quotes and place the variables within curly braces. If you want to use single quotes for the string concatenation, you will need to concatenate the variables separately using the period (.) operator. 

// Using double quotes for string concatenation with variable interpolation
$name = "John";
$greeting = "Hello, {$name}!";

// Using single quotes for string concatenation without variable interpolation
$name = "John";
$greeting = 'Hello, ' . $name . '!';

Keywords

PHP single quotes double quotes string concatenation escape characters

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