Single vs. Double Quotes

PHP offers two ways to enclose strings: single quotes (') and double quotes ("). While seemingly interchangeable at first glance, they possess distinct behaviors:

Understanding the Differences

1. Variable Interpolation

Double quotes allow variable interpolation, embedding variables directly within the string. For example:

    $name = "Kristi";
    echo "Hello, my name is $name."; // Outputs: Hello, my name is Kristi.
    

Single quotes, on the other hand, interpret the string literally. To include variables, you'd need concatenation:

    $name = "Kristi";
    echo 'Hello, my name is ' . $name . '.'; // Outputs: Hello, my name is Kristi.
    

2. Escape Sequences

Double quotes recognize predefined escape sequences like \n for newlines and \" for escaping quotes within the string.

    echo "This is a string with a newline \n and an escaped quote \".";
    

Single quotes ignore escape sequences, displaying all characters literally.

    echo 'This is a string with a literal \n and escaped quote \"'; // Outputs: This is a string with a literal \n and escaped quote ".
    

3. Performance

Single quotes generally perform slightly better than double quotes due to simpler parsing.

Choosing the Right Quote

The choice depends on your needs:

• Use double quotes when you need variable interpolation or escape sequences.
• Use single quotes when you want the string interpreted literally with no variable substitution or escape sequences, or for slightly better performance in non-critical sections.

Understanding these distinctions will enhance your code readability and maintainability.