What operator is used for string concatenation in PHP?

PHP uses the dot operator (.) for string concatenation, and the dot-equals operator (.=) for concatenating and appending directly to an existing string variable.

What is the difference between Heredoc and Nowdoc syntax?

Heredoc (<<<EOD ... EOD;) acts like double-quoted strings, allowing variable interpolation inside large multi-line blocks of text. Nowdoc (<<<'EOD' ... EOD;) acts like single-quoted strings, treating all content literally without variable parsing.

How do I count characters in a multibyte UTF-8 string?

Standard strlen() counts raw bytes, which can miscount multi-byte characters like emojis or Hindi/Devanagari text. Use mb_strlen() for accurate multi-byte UTF-8 character counts.

PHP Strings: Creation, Manipulation, Heredoc & Built-In String Functions

Q: What is the difference between Heredoc and Nowdoc syntax?

Heredoc (<<<EOD ... EOD;) acts like double-quoted strings, allowing variable interpolation inside large multi-line blocks of text. Nowdoc (<<<'EOD' ... EOD;) acts like single-quoted strings, treating all content literally without variable parsing.

Q: How do I count characters in a multibyte UTF-8 string?

Standard strlen() counts raw bytes, which can miscount multi-byte characters like emojis or Hindi/Devanagari text. Use mb_strlen() for accurate multi-byte UTF-8 character counts.

A string is an ordered sequence of characters, such as "Hello World" or "Veewom Educational Tutorial". Strings represent the most frequently manipulated data type in web applications, used for user names, emails, article paragraphs, and HTML templates. In this guide, you will master string creation, the string concatenation operator, essential built-in string functions, and advanced multi-line Heredoc and Nowdoc syntax.

Creating Strings in PHP: Single vs Double Quotes

You can define strings using four distinct mechanisms in PHP:

Single Quotes ('...'): High performance, treats escape sequences and variable names literally.
Double Quotes ("..."): Supports variable expansion (interpolation) and special escape sequences like \n (newline) and \t (tab).
Heredoc Syntax (<<<IDENTIFIER ... IDENTIFIER;): Perfect for large multi-line blocks of HTML/text with variable interpolation.
Nowdoc Syntax (<<<'IDENTIFIER' ... IDENTIFIER;): Multi-line literal text without variable parsing.

The Concatenation Operators: Dot (`.`) and Append (`.=`)

Unlike languages like JavaScript or Python that use the plus symbol (+) for string joining, PHP uses the dot (.) operator. Using + in PHP will attempt to perform arithmetic addition!

<?php
    $firstName = "Arun";
    $lastName = "Kumar";

    // Concatenation with dot operator
    $fullName = $firstName . " " . $lastName;
    echo "Full Name: " . $fullName . "<br>"; // Arun Kumar

    // Concatenating and assigning with .=
    $greeting = "Good Morning, ";
    $greeting .= $fullName;
    $greeting .= "! Welcome to PHP class.";
    echo $greeting;
?>

Top 10 Built-In PHP String Functions (University Exam Favorites)

Function	Description	Example & Output
`strlen($str)`	Returns string length in bytes/characters.	`strlen("Veewom")` → `6`
`str_word_count($str)`	Counts total number of words.	`str_word_count("PHP is great")` → `3`
`strrev($str)`	Reverses the string characters.	`strrev("Hello")` → `"olleH"`
`strpos($str, $search)`	Returns 0-based index position of first match.	`strpos("Veewom", "wom")` → `3`
`str_replace($f, $r, $str)`	Replaces all occurrences of search string.	`str_replace("World", "PHP", "Hello World")` → `"Hello PHP"`
`strtolower($str)`	Converts all letters to lowercase.	`strtolower("VEEWOM")` → `"veewom"`
`strtoupper($str)`	Converts all letters to uppercase.	`strtoupper("veewom")` → `"VEEWOM"`
`trim($str)`	Strips whitespace from start and end.	`trim(" clean ")` → `"clean"`
`substr($str, $start, $len)`	Extracts a substring slice.	`substr("Veewom", 0, 3)` → `"Vee"`
`explode($del, $str)`	Splits string into array by delimiter.	`explode(",", "red,blue,green")` → `["red", "blue", "green"]`

Multi-Line Strings: Heredoc vs Nowdoc

When generating complex HTML emails or database SQL queries, Heredoc and Nowdoc avoid messy quote escaping:

<?php
    $student = "Sunil";
    $examDate = "December 15, 2026";

    // HEREDOC: Parses variables ($student, $examDate)
    $emailBody = <<<EMAIL
    <div class="notice">
        <h3>Exam Notification for $student</h3>
        <p>Your semester examination is scheduled on $examDate.</p>
    </div>
EMAIL;

    echo $emailBody;

    // NOWDOC: Treats text literally (enclosed in single quotes)
    $codeSnippet = <<<'CODE'
    The variables $student and $examDate will NOT be replaced here.
CODE;

    echo $codeSnippet;
?>

BCA / CS University Exam Corner

High-Frequency Exam Question:

Q: Why must you check strpos() with strict comparison (=== false)?
A: If the matching substring is located at the very start of the string (index 0), an unstrict comparison like if (strpos(...) == false) will evaluate index 0 to false, wrongly indicating that the match was not found! Always check: if (strpos(...) !== false).

Interactive Student Practice Session

Exercise 7.1: Write a PHP script that checks whether an input string is a Palindrome (reads the same backwards and forwards, e.g. "madam" or "radar") using strrev().

Exercise 7.2: Write a script that cleans an email input: trims whitespace, converts it to lowercase, and verifies it contains the "@" character using strpos().