CSV file reading and writing in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code reading a CSV file?

Consider the following PHP code that reads a CSV file and prints each row as a JSON string.

$file = fopen('data.csv', 'r');
while (($row = fgetcsv($file)) !== false) {
    echo json_encode($row) . "\n";
}
fclose($file);

Assuming data.csv contains these lines:

apple,banana,cherry
1,2,3
x,y,z

What will be the output?

PHP

$file = fopen('data.csv', 'r');
while (($row = fgetcsv($file)) !== false) {
    echo json_encode($row) . "\n";
}
fclose($file);

A

["apple","banana","cherry"]
["1","2","3"]
["x","y","z"]

B

Error: Cannot open file

C

["apple,banana,cherry"]
["1,2,3"]
["x,y,z"]

D

apple,banana,cherry
1,2,3
x,y,z

💡 Hint

Remember that fgetcsv returns an array of fields for each line.

The fgetcsv function reads each line and splits it by commas into an array. Then json_encode converts the array to a JSON string. So each line is printed as a JSON array of strings.

❓ Predict Output

intermediate

What does this PHP code write to a CSV file?

Given this PHP code that writes data to a CSV file:

$data = [
    ['Name', 'Age', 'City'],
    ['Alice', 30, 'New York'],
    ['Bob', 25, 'Los Angeles']
];
$file = fopen('output.csv', 'w');
foreach ($data as $row) {
    fputcsv($file, $row);
}
fclose($file);

What will be the content of output.csv after running this code?

PHP

$data = [
    ['Name', 'Age', 'City'],
    ['Alice', 30, 'New York'],
    ['Bob', 25, 'Los Angeles']
];
$file = fopen('output.csv', 'w');
foreach ($data as $row) {
    fputcsv($file, $row);
}
fclose($file);

A

Name,Age,City
Alice,30,New York
Bob,25,Los Angeles

B

["Name","Age","City"]
["Alice",30,"New York"]
["Bob",25,"Los Angeles"]

C

Name;Age;City
Alice;30;New York
Bob;25;Los Angeles

D

Error: Cannot write to file

💡 Hint

fputcsv writes arrays as comma-separated lines by default.

The fputcsv function writes each array as a line with comma-separated values. So the file will have three lines with commas separating the fields.

🔧 Debug

advanced

Why does this PHP code reading CSV raise a warning?

Look at this PHP code snippet:

$file = fopen('data.csv', 'r');
while ($row = fgetcsv($file)) {
    print_r($row);
}
fclose($file);

Sometimes it raises a warning: Warning: fgetcsv() expects parameter 1 to be resource, bool given. Why?

PHP

$file = fopen('data.csv', 'r');
while ($row = fgetcsv($file)) {
    print_r($row);
}
fclose($file);

A Because fgetcsv requires a string filename, not a resource.

B Because print_r cannot print arrays returned by fgetcsv.

C Because fopen failed and returned false, so fgetcsv got a boolean instead of a file resource.

D Because fclose was called before the loop started.

💡 Hint

Check the return value of fopen before using it.

If fopen fails (e.g., file missing), it returns false. Passing false to fgetcsv causes the warning because it expects a file resource.

📝 Syntax

advanced

Which option correctly reads a CSV file into an array of rows?

Which PHP code snippet correctly reads all rows from a CSV file data.csv into an array $rows?

A

$rows = [];
$file = fopen('data.csv', 'r');
while ($row = fgetcsv($file)) {
    $rows[] = $row;
}
fclose($file);

B

$rows = [];
$file = fopen('data.csv', 'r');
while (($row = fgetcsv($file)) !== false) {
    $rows[] = $row;
}
fclose($file);

C

$rows = [];
$file = fopen('data.csv', 'r');
while ($row = fgetcsv($file) !== false) {
    $rows[] = $row;
}
fclose($file);

D

$rows = [];
$file = fopen('data.csv', 'r');
while ($row !== false = fgetcsv($file)) {
    $rows[] = $row;
}
fclose($file);

💡 Hint

Remember operator precedence and correct syntax for while loops.

Option B uses parentheses to ensure fgetcsv($file) is called and its result compared to false. Option B misses strict comparison and may add false as a row. Option B has wrong operator precedence, assigning boolean to $row. Option B is invalid syntax.

🚀 Application

expert

How to write a CSV file with semicolon delimiter in PHP?

You want to write a CSV file data.csv where fields are separated by semicolons (;) instead of commas. Which code snippet correctly does this?

A

$file = fopen('data.csv', 'w');
fputcsv($file, ['a', 'b', 'c']);
fclose($file);

B

$file = fopen('data.csv', 'w');
fputcsv($file, ['a', 'b', 'c'], ',');
fclose($file);

C

$file = fopen('data.csv', 'w');
fwrite($file, 'a;b;c\n');
fclose($file);

D

$file = fopen('data.csv', 'w');
fputcsv($file, ['a', 'b', 'c'], ';');
fclose($file);

💡 Hint

Check the third parameter of fputcsv for delimiter.

Option D uses fputcsv with the third argument set to ; to change the delimiter. Option D uses comma, so default delimiter. Option D uses default comma delimiter. Option D writes a string manually, which works but is not using fputcsv.