Single or Double Quotes in PHP Strings: What's the Difference?

String Quotation Marks in PHP: Single vs. Double

In PHP, strings can be enclosed in either single or double quotation marks. Understanding the differences between these two is crucial for effective coding.

Single-Quoted Strings

• Parse as a literal string, with no variable interpolation or escape sequence interpretation (except for escaping characters and backslashes).
• This means single-quoted strings display exactly what is enclosed, providing a more predictable output.

Double-Quoted Strings

• Allow variable interpolation and escape sequence interpretation (including regular expressions).
• Curly braces can be used to isolate variable names for evaluation within the string.
• Escape characters (e.g., n for newline) and double quotes require escaping within double-quoted strings.

Additional String Syntax

In addition to single and double quotation marks, PHP offers two additional string syntax types:

• Heredoc: Begins with <<< followed by an identifier, multiline string, and closing identifier. Allows for variable interpolation and escape sequences.
• Nowdoc: Similar to heredoc, but behaves like a single-quoted string with no parsing of variables or escape sequences.

Speed Performance

Contrary to popular belief, there is no significant difference in execution speed between single and double-quoted strings. Both are interpreted into opcodes during script execution, with minimal impact on runtime performance.

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