How PHP executes on the server - Practice Exercises

Challenge - 5 Problems

❓ Predict Output

intermediate

PHP Script Execution Output

What is the output of this PHP code when executed on a server?

PHP

<?php
function test() {
    static $count = 0;
    $count++;
    return $count;
}

echo test();
echo test();
echo test();
?>

A 321

B 111

C 123

D Syntax Error

💡 Hint

Static variables inside functions keep their value between calls.

The static variable $count inside the function test() retains its value between calls, so it increments each time test() is called, producing 1, then 2, then 3, output as '123'.

🧠 Conceptual

intermediate

PHP Server Execution Flow

Which step correctly describes what happens first when a PHP file is requested by a browser?

A The browser executes the PHP code directly.

B The PHP code is compiled into a binary executable on the client.

C The server sends the PHP code as plain text to the browser.

D The PHP interpreter parses and executes the PHP code on the server.

💡 Hint

Remember where PHP code runs: server or client?

PHP code runs on the server. When a PHP file is requested, the server uses the PHP interpreter to parse and execute the code, then sends the resulting output (usually HTML) to the browser.

🔧 Debug

advanced

Identify the Error in PHP Execution

What error will this PHP code produce when executed on the server?

PHP

<?php
$number = 10;
if ($number = 5) {
    echo "Number is five.";
} else {
    echo "Number is not five.";
}
?>

A Outputs: Number is five.

B Outputs: Number is not five.

C Syntax Error due to assignment in if condition.

D Runtime Error: Undefined variable.

💡 Hint

Check the difference between '=' and '==' in conditions.

The if condition uses '=' which assigns 5 to $number and returns true, so the if block runs and outputs 'Number is five.'. This is a common mistake where '==' (comparison) was intended.

📝 Syntax

advanced

PHP Syntax Error Identification

Which option contains a syntax error that will prevent PHP from executing the script?

PHP

<?php
function greet($name) {
    echo "Hello, $name!";
}
greet("Alice");
?>

A

<?php
function greet($name) {
    echo "Hello, $name!";
}
greet("Alice"
?>

B

<?php
function greet($name) {
    echo "Hello, $name!";
}
greet("Alice");
?>

C

<?php
function greet($name) {
    echo "Hello, $name!";
}
greet("Alice");

D

>?
;)"ecilA"(teerg
}
;"!eman$ ,olleH" ohce    
{ )eman$(teerg noitcnuf
php?<

💡 Hint

Look for missing parentheses or semicolons.

Option A is missing the closing parenthesis in the greet function call, causing a syntax error and preventing execution.

🚀 Application

expert

PHP Output Buffering Behavior

What will be the output of this PHP code when executed on the server?

PHP

<?php
ob_start();
echo "Start-";
ob_clean();
echo "End";
ob_end_flush();
?>

A Start-End

B End

C Start

D No output

💡 Hint

ob_clean() clears the output buffer before sending it.

The output buffer starts and 'Start-' is echoed but then ob_clean() clears the buffer, so 'Start-' is removed. Then 'End' is echoed and finally ob_end_flush() sends the buffer content, which is 'End'.

Practice

1. What happens when a PHP file is requested by a browser?

easy

A. The PHP code is downloaded as a file to the browser

B. The browser runs the PHP code directly

C. The server runs the PHP code and sends the output to the browser

D. The server sends the PHP code as plain text to the browser

Solution

1. Step 1: Understand PHP execution location

   PHP code runs on the server, not in the browser.

2. Step 2: Identify what the browser receives

   The server sends only the output (usually HTML) to the browser, not the PHP code itself.

3. Final Answer:

   The server runs the PHP code and sends the output to the browser -> Option C

4. Quick Check:

   PHP runs on server = A [OK]

Hint: Remember: PHP runs on server, browser gets output only [OK]

Common Mistakes:

• Thinking browser executes PHP code
• Expecting PHP code to be visible in browser source
• Confusing PHP with client-side languages like JavaScript

2. Which of the following is the correct way to start a PHP block in a file?

easy

A.

B.

C.

D.

Solution

1. Step 1: Recall PHP opening tags

   The standard and recommended way to start PHP code is with

2. Step 2: Check each option

   uses which is correct. Others are invalid or incomplete tags.

3. Final Answer:

   -> Option A

4. Quick Check:

   Standard PHP tag = B [OK]

Hint: PHP code always starts with php [OK]

Common Mistakes:

• Using short tags like which may be disabled
• Confusing PHP tags with HTML or script tags
• Missing the 'php' keyword after

3. What will be the output of this PHP code when accessed via a browser?

<?php
echo "Hello, " . "world!";
?>

medium

A. Syntax Error

B. echo "Hello, " . "world!";

C. Hello, . world!

D. Hello, world!

Solution

1. Step 1: Understand echo statement

   The echo command outputs the combined string "Hello, world!" to the browser.

2. Step 2: Confirm string concatenation

   The dot operator joins "Hello, " and "world!" correctly without errors.

3. Final Answer:

   Hello, world! -> Option D

4. Quick Check:

   echo concatenates strings = D [OK]

Hint: echo prints combined strings directly [OK]

Common Mistakes:

• Expecting PHP code to show in browser
• Confusing concatenation operator
• Thinking dot prints as text

4. Identify the error in this PHP code snippet:

<?php
echo "Welcome to PHP!"
?>

medium

A. Missing quotes around string

B. Missing semicolon after echo statement

C. Incorrect PHP opening tag

D. Using echo instead of print

Solution

1. Step 1: Check syntax of echo statement

   PHP statements must end with a semicolon ; to separate commands.

2. Step 2: Locate missing semicolon

   The echo line lacks a semicolon at the end, causing a syntax error.

3. Final Answer:

   Missing semicolon after echo statement -> Option B

4. Quick Check:

   Statements need ; = C [OK]

Hint: Always end PHP statements with a semicolon ; [OK]

Common Mistakes:

• Forgetting semicolon at line end
• Confusing PHP tags with HTML tags
• Assuming echo doesn't need semicolon

5. You want to create a PHP page that shows the current year dynamically. Which code snippet correctly does this?

<?php
// Options:
// A: echo date("Y");
// B: echo "date(Y)";
// C: echo date(Y, Y);
// D: echo "Y";
?>

hard

A. echo date("Y");

B. echo "date(Y)";

C. echo date(Y, Y);

D. echo "Y";

Solution

1. Step 1: Understand PHP date function usage

   The date function requires the format string in quotes to return the current year.

2. Step 2: Evaluate each option

   echo date("Y"); correctly calls date("Y") to output the year. echo "date(Y)"; prints the string literally. echo date(Y, Y); misses quotes causing undefined constants and wrong output (1970). echo "Y"; prints letter Y only.

3. Final Answer:

   echo date("Y"); -> Option A

4. Quick Check:

   Correct date format string = A [OK]

Hint: Use quotes around format in date() function [OK]

Common Mistakes:

• Omitting quotes around format string
• Printing function call as string
• Confusing output with literal text