PHP Syntax

PHP Tags

PHP code must live between <?php and ?> tags. Everything outside is treated as plain HTML and sent to the browser as-is.

<h1>This is plain HTML</h1>
<?php
    echo "This is PHP output";
?>
<p>More plain HTML</p>
<?= "Short echo PHP" ?>

Three tag styles

Statements & Semicolons

Every PHP statement ends with a semicolon ;. A statement is one complete instruction.

<?php
$name = "Ruban";          // assignment statement
echo $name;               // output statement
echo "Hello";  echo $name;// multiple statements on one line - legal but ugly

// You can split a long statement across multiple lines
$message = "This is a "
         . "long string "
         . "split into lines";

The line does not matter to PHP - the semicolon does. Forget a semicolon and you get a parse error pointing to the next line.

Comments

PHP supports three styles of comments. Use them generously - your future self will thank you.

<?php
// Single-line comment (C++ style) - most common

# Single-line comment (shell style) - rarely used

/*
   Multi-line comment
   spans across multiple lines
*/

/**
 * Doc comment (PHPDoc) - used to document
 * functions, classes, and methods.
 *
 * @param string $name The user name
 * @return string Welcome message
 */
function welcome(string $name): string {
    return "Hello, $name";
}

Case Sensitivity Rules

PHP has unusual case-sensitivity rules. Memorize them now to save future debugging:

Whitespace & Line Breaks

PHP ignores whitespace between tokens. These all work identically:

<?php
$total = 10 + 5;
$total=10+5;
$total
    =
    10
    +
    5
    ;

Always use the readable version. Most teams follow PSR-12 which mandates 4-space indentation, no tabs.

Alternative Syntax for HTML

When mixing PHP into HTML, curly braces become hard to track. PHP provides an alternative syntax using : and end* keywords:

<ul>
<?php foreach ($users as $user): ?>
    <li>
        <?= htmlspecialchars($user["name"]) ?>
        <?php if ($user["admin"]): ?>
            <strong>(Admin)</strong>
        <?php endif; ?>
    </li>
<?php endforeach; ?>
</ul>

Each control structure has an end keyword: endif, endfor, endforeach, endwhile, endswitch.

Language Constructs vs Functions

PHP has two kinds of callable things, and they look almost identical:

<?php
// Language constructs - parentheses are optional
echo "Hello";
echo("Hello");        // works
print "Hello";
include "file.php";

// Real functions - parentheses required
strlen("Hello");
date("Y-m-d");

Language constructs (echo, print, include, require, isset, unset, empty) are part of the language grammar, so they don't need parentheses. Real functions always need them.

Syntax Best Practices

1. Always use <?php, never <?
2. Omit the closing ?> in pure PHP files
3. Use 4 spaces for indentation (PSR-12), never tabs
4. One statement per line - your diff tool and your eyes will thank you
5. Lowercase keywords - if, while, true, null
6. PascalCase classes, camelCase methods, snake_case variables/files
7. Comment the why, not the what - the code shows what, comments explain why

Next Steps

The syntax foundations are in place. Now move on to working with data:

• Variables - store values
• Data types - integers, strings, arrays
• Operators - arithmetic, comparison, logical