How to Use String Interpolation in PHP — Phpflow.com

Parvez Alam
3 min readJan 10, 2024

We’ll look at PHP string interpolation with an example of best practices in this article. Developers can directly embed variables into strings with the help of string interpolation, which also makes variable concatenation easier and makes code easier to read.

What is String Interpolation

The process of evaluating variables and expressions within a string and replacing placeholders with their actual values is known as string interpolation. PHP supports two main methods of string interpolation: double-quoted strings and heredoc syntax.

Sample Example Using concatenation:

$f_name = "Adam"; $l_name = "Joe"; $message = "Hello, My Name is " . $f_name . " " . $l_name . ".";

Using string interpolation:

$message = "Hello, You are first name $f_name and last name is l_name.";

in the above code, We have two variables $name and $age, and directly embedded within the string using the $ symbol.

Benefits of String Interpolation:

  • Readability and Conciseness: It enhances code readability by eliminating the need for explicit concatenation.
  • Improved Code Maintainability: It improves code Maintainability without being distracted by concatenation operators.
  • Enhanced String Formatting: It maintains formatting while enabling effortless integration of variables into complex strings.

Single-quoted strings

Single-quoted strings do not support variable interpolation in PHP. You can use . operator in single-quoted strings to concatenate variables with the string.

$f_name = "Adam"; $l_name = "Joe"; $message = 'Hello, You are first name'. $f_name .and last name is '.$l_name; echo $message;

Output:

Hello, You are first name Adam and last name is Joe.

String Interpolation in PHP

Let’s start String Interpolation in PHP with some examples and discuss the benefits of it over string concatenation. Here, We’ll cover the following ways to interpolate string:

Double quoted strings:

You can use double quotes for string interpolation in PHP. When a string is enclosed in double quotes, PHP will replace variables with their values within the string. Here’s an example:

$f_name = "Adam"; $l_name = "Joe"; $message = "Hello, You are first name $f_name and last name is $l_name."; echo $message;

Output:

Hello, You are first name Adam and last name is Joe.

Heredoc syntax:

You can use Heredoc syntax to do string interpolation in PHP. Heredoc allows you to specify a multi-line string without the need for single or double quotes while maintaining all of the whitespace, including line breaks.

$f_name = "Adam"; $l_name = "Joe"; $message = <<<EOT Hello, my name is $f_name $l_name. This is a multiline string using heredoc. EOT; echo $message;

In this example, <<<EOT starts the heredoc string, and EOT; ends it. The variables $f_name and $l_name are interpolated within the heredoc string. The output will be:

Hello, my name is Adam Joe. This is a multiline string using heredoc.

Heredoc is useful whenever you need to maintain formatting without escaping special characters in large text blocks or multiline strings.

Some More Example: PHP String Interpolation

Let’s discuss some examples of string interpolation using PHP.

Escape Special Characters

You can also escape special characters in the time of interpolation. The variables contain characters like quotes or backslashes treated as a normal characters.

$message = "Hello! I am adam!"; echo "The message is: \"$message\"";

Output:

The message is: "Hello! I am adam!"

Use Curly Braces for Complex Expressions

It’s better to use curly braces to clearly define the variable scope for more complex expressions inside interpolated strings.

$n1 = 20; $n2 = 10; echo "The sume are: \${$n1 * $n2}";

Output:

The sum is: 40

Conclusion:

We have learned about string interpolation in PHP. You can use string concatenation for simple string manipulation, but for more complex strings you need to use double-quoted or heredoc syntax to manipulate string. The string interpolation enhances code readability and maintainability.

Originally published at https://www.phpflow.com on January 10, 2024.

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Parvez Alam

Hey, I am Parvez Alam. A software developer since 2009. I love learning and sharing knowledge. https://www.phpflow.com/