PHP Syntax & Structure
In this page:
<?php
statement_one; // each statement ends with a semicolon
statement_two;
if (condition) {
// block of code in braces
}
?>Semicolons
PHP uses a semicolon to mark the end of each statement, the same way a period ends a sentence — it's how the interpreter knows one instruction has finished and the next one is starting.
Omitting it is one of the most common beginner errors, and it usually produces a 'parse error, unexpected token' pointing at the *next* line, not the missing one.
Example: Semicolons
<?php
echo "First statement";
echo "Second statement";
// Each statement ends with a semicolon, like a period ends a sentence
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Case Sensitivity in PHP
Language keywords and built-in function names in PHP (if, echo, strlen) are case-insensitive, so ECHO and echo behave identically.
Variable names are the opposite: $Name and $name are two completely different variables, so consistent casing matters a lot more for variables than for keywords.
Example: Case Sensitivity in PHP
<?php
ECHO "Keywords are case-insensitive.\n";
// Declare `$Name`, set to "Alice"
$Name = "Alice";
// Declare `$name`, set to "Bob"
$name = "Bob";
// Print "$Name and $name are different variables." to the output
echo "$Name and $name are different variables.";
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Braces and Blocks
Curly braces { } mark where a block of code begins and ends — the body of a function, the branches of an if/else, or the body of a loop.
Everything inside the braces executes together as a unit, which is what lets you group multiple statements under a single condition or loop.
Example: Braces and Blocks
<?php
// Check whether `true`
if (true) {
// Print "Statement one in the block.\n" to the output
echo "Statement one in the block.\n";
// Print "Statement two in the block.\n" to the output
echo "Statement two in the block.\n";
}
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Whitespace and Layout
PHP doesn't care about indentation or extra blank lines the way some languages do — they're purely for human readability.
That said, consistent indentation makes nested blocks (loops inside conditions inside functions) far easier to read at a glance, so most style guides enforce it even though the interpreter doesn't require it.
Example: Whitespace and Layout
<?php
// Print "Indentation is ignored by PHP" to the output
echo "Indentation is ignored by PHP";
// Print "but blank lines don't matter either." to the output
echo "but blank lines don't matter either.";
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Code Nesting
Because PHP tags can appear anywhere inside an HTML file, you can drop small PHP snippets directly into a template — printing a username in a <h1>, say — without converting the whole file to PHP.
The server only executes what's between <?php and ?>; the surrounding HTML passes through untouched.
Example: Code Nesting
<?php $username = "Alice"; ?>
<?php // The PHP tag below prints $username directly into the HTML ?>
<h1>Welcome, <?php echo $username; ?></h1>
<p>This HTML passes through untouched.</p>Login to try C/C++/Java/PHP code in the editor
- Forgetting the semicolon at the end of a statement, so PHP reports a parse error on the following line rather than where the semicolon is missing.
- Writing
$Namein one place and$namein another, since variable names are case-sensitive and the second is a different, undefined variable. - Leaving a
{unclosed or mismatched, causing a 'unexpected end of file' parse error far from the real mistake.
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