Strings

Introduction

Strings are sequences of characters — text — and they are one of the most frequently used data types in any PHP script, from displaying a greeting to building an HTML page. PHP gives you more than one way to create a string, and the way you choose changes how PHP treats the text inside it.

This lesson covers how to create and work with strings themselves. PHP's large library of built-in string functions — for searching, replacing, splitting, and transforming text — gets its own dedicated lesson right after this one.

Creating Strings

The simplest way to create a string in PHP is to wrap text in either single quotes (') or double quotes ("). Both produce a string, but they behave differently once variables or special characters are involved.

<?php
    $single = 'Hello, World!';
    $double = "Hello, World!";

    echo $single;
    echo "\n";
    echo $double;
?>

Hello, World!
Hello, World!

Single vs Double Quotes

The difference only becomes visible once a variable or an escape sequence appears inside the string. Double-quoted strings interpolate variables (substituting in their value) and interpret escape sequences like \n for a newline. Single-quoted strings treat almost everything literally.

<?php
    $name = "Amol";

    echo "Hello, $name!\n";   // Double quotes: variable interpolated, \n becomes a newline
    echo 'Hello, $name!\n';    // Single quotes: printed literally, no interpolation
?>

Hello, Amol!
Hello, $name!\n

Variable Interpolation

Interpolation means a variable's value is automatically substituted into a double-quoted string without needing to concatenate it manually. For array elements or object properties, curly braces can be used to make the boundaries of the expression explicit.

<?php
    $name = "Amol";
    $age = 25;

    echo "Name: $name, Age: $age\n";

    $user = ["name" => "Priya"];
    echo "Welcome, {$user['name']}!\n"; // curly braces clarify the expression
?>

Name: Amol, Age: 25
Welcome, Priya!

Escape Sequences

Escape sequences let you include special characters — like a newline or a literal quote — inside a string. They are only interpreted inside double-quoted strings (with the exception of \\ and \', which also work inside single quotes).

<?php
    echo "Line one\nLine two\n";
    echo "She said \"hello\".\n";
    echo "Price: \$100\n"; // \$ prevents interpolation attempt
?>

Line one
Line two
She said "hello".
Price: $100

String Concatenation

You already saw this in the Operators lesson: the . operator joins strings together, and .= appends a string onto an existing variable.

<?php
    $first = "Code";
    $second = "Journey";

    $combined = $first . $second;
    echo $combined; // "PrograMinds"

    $combined .= "!";
    echo $combined; // "PrograMinds!"
?>

PrograMinds
PrograMinds!

Accessing Characters by Index

A PHP string can be treated like an array of characters. Square-bracket notation, $str[0], accesses the character at a given position, starting from index 0. Negative indexes count backward from the end of the string.

<?php
    $word = "PHP";

    echo $word[0]; // "P"
    echo $word[1]; // "H"
    echo $word[2]; // "P"
    echo $word[-1]; // "P" (last character)

    echo strlen($word); // 3 (a preview of string functions - covered in depth next lesson)
?>

PHP
P3

Heredoc and Nowdoc

For strings spanning multiple lines, especially ones mixing lots of text and variables, PHP offers heredoc syntax — introduced with <<<IDENTIFIER — which behaves like a double-quoted string (interpolating variables) but without needing to escape every quote inside it. Nowdoc, written with <<<'IDENTIFIER' (quoted), behaves like a single-quoted string instead, with no interpolation at all.

<?php
    $name = "Amol";

    $message = <<<EOT
    Hello, $name!
    This is a multi-line string.
    It supports interpolation just like double quotes.
    EOT;

    echo $message;
?>

Hello, Amol!
This is a multi-line string.
It supports interpolation just like double quotes.

Nowdoc works identically but with single quotes around the opening identifier, and treats its contents literally, with no variable interpolation — the closing identifier still must appear on its own line, matching the indentation of the surrounding code.

<?php
    $text = <<<'EOT'
    Hello, $name!
    This is treated literally - no interpolation.
    EOT;

    echo $text;
?>

Hello, $name!
This is treated literally - no interpolation.

Common Mistakes

Best Practices

Frequently Asked Questions

Key Takeaways

Summary

Strings are everywhere in PHP, and knowing exactly how single quotes, double quotes, interpolation, and concatenation behave will save you from a lot of subtle output bugs. With the fundamentals of creating and combining strings in place, the next lesson dives into PHP's extensive built-in string function library for actually transforming and analyzing text.