CSV file reading and writing in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a CSV file for reading.

PHP

<?php
$handle = fopen('data.csv', '[1]');
?>

Drag options to blanks, or click blank then click option'

A'a'

B'w'

C'r'

D'x'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' or 'a' mode which are for writing or appending.

Forgetting to put the mode in quotes.

To read a CSV file, you open it in read mode using 'r'.

2fill in blank

medium

Complete the code to read a line from the CSV file as an array.

PHP

<?php
$handle = fopen('data.csv', 'r');
$row = fgetcsv([1]);
?>

Drag options to blanks, or click blank then click option'

A$file

B$handle

C$csv

D$data

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable that was not assigned to fopen.

Passing a string filename instead of the file handle.

The variable holding the file pointer is $handle, which is passed to fgetcsv to read a line.

3fill in blank

hard

Fix the error in the code to write an array as a CSV line.

PHP

<?php
$handle = fopen('output.csv', 'w');
fputcsv([1], ['apple', 'banana', 'cherry']);
fclose($handle);
?>

Drag options to blanks, or click blank then click option'

A$csv

B$file

C$data

D$handle

Attempts:

3 left

💡 Hint

Common Mistakes

Passing an undefined variable to fputcsv.

Confusing the file handle variable name.

fputcsv requires the file handle as the first argument, which is $handle here.

4fill in blank

hard

Fill both blanks to read all lines from a CSV file into an array.

PHP

<?php
$handle = fopen('data.csv', 'r');
$data = [];
while (($row = fgetcsv([1])) [2] false) {
    $data[] = $row;
}
fclose($handle);
?>

Drag options to blanks, or click blank then click option'

A$handle

B$file

C!==

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '!==' in the while condition.

Using wrong variable for the file handle.

We use $handle as the file pointer and check that fgetcsv does not return false to continue reading lines.

5fill in blank

hard

Fill all three blanks to write multiple rows to a CSV file using a loop.

PHP

<?php
$rows = [
    ['John', 'Doe', 30],
    ['Jane', 'Smith', 25],
    ['Bob', 'Johnson', 40]
];
$handle = fopen('people.csv', 'w');
foreach ([1] as [2]) {
    fputcsv([3], $row);
}
fclose($handle);
?>

Drag options to blanks, or click blank then click option'

A$rows

B$row

C$handle

D$data

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names in the foreach loop.

Passing wrong variable to fputcsv.

The foreach loops over $rows as $row, and fputcsv writes each $row to the file handle $handle.

Practice

1. Which PHP function is used to read a line from a CSV file and parse it into an array?

easy

A. fgetcsv()

B. fputcsv()

C. fread()

D. fwrite()

Solution

1. Step 1: Understand CSV reading functions

   PHP provides fgetcsv() to read a line from a CSV file and convert it into an array of values.

2. Step 2: Differentiate from writing functions

   fputcsv() writes arrays to CSV files, while fread() and fwrite() handle raw file reading/writing without CSV parsing.

3. Final Answer:

   fgetcsv() -> Option A

4. Quick Check:

   Read CSV line as array = fgetcsv() [OK]

Hint: Use fgetcsv() to read CSV lines into arrays [OK]

Common Mistakes:

• Confusing fgetcsv() with fputcsv()
• Using fread() which reads raw data, not CSV parsed
• Trying to read CSV without parsing into arrays

2. Which of the following is the correct way to open a CSV file for writing in PHP?

easy

A. $file = fopen('data.csv', 'r');

B. $file = fopen('data.csv', 'rw');

C. $file = fopen('data.csv', 'w');

D. $file = fopen('data.csv', 'x');

Solution

1. Step 1: Understand fopen modes

   Mode 'w' opens a file for writing and truncates it if it exists, perfect for writing CSV files.

2. Step 2: Check other modes

   'r' is read-only, 'rw' is invalid, 'x' creates a new file but fails if it exists.

3. Final Answer:

   $file = fopen('data.csv', 'w'); -> Option C

4. Quick Check:

   Open file for writing = 'w' mode [OK]

Hint: Use 'w' mode in fopen() to write files [OK]

Common Mistakes:

• Using 'r' mode when intending to write
• Using invalid mode 'rw'
• Using 'x' which fails if file exists

3. What will be the output of the following PHP code snippet?

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

Assuming the first line of data.csv is:
John,Doe,30

medium

A. Array ( [0] => John [1] => Doe [2] => 30 )

B. John,Doe,30

C. Array ( [0] => 'John,Doe,30' )

D. Error: Cannot read file

Solution

1. Step 1: Understand fgetcsv() output

   fgetcsv() reads one CSV line and returns an array splitting values by commas.

2. Step 2: Analyze given CSV line

   The line 'John,Doe,30' splits into array elements: 'John', 'Doe', and '30'.

3. Final Answer:

   Array ( [0] => John [1] => Doe [2] => 30 ) -> Option A

4. Quick Check:

   fgetcsv() splits CSV line into array [OK]

Hint: fgetcsv() returns array of CSV fields from one line [OK]

Common Mistakes:

• Expecting a string instead of an array
• Assuming fgetcsv returns raw line string
• Not closing the file after reading

4. Identify the error in the following PHP code that writes data to a CSV file:

$file = fopen('output.csv', 'r');
fputcsv($file, ['Alice', 'Smith', 25]);
fclose($file);

medium

A. Array syntax is incorrect

B. fputcsv() cannot write arrays

C. Missing fclose() call

D. File opened in read mode instead of write mode

Solution

1. Step 1: Check fopen mode

   The file is opened with 'r' (read) mode, which does not allow writing.

2. Step 2: Understand fputcsv requirements

   fputcsv() requires the file to be opened in write ('w') or append ('a') mode to write data.

3. Final Answer:

   File opened in read mode instead of write mode -> Option D

4. Quick Check:

   Open file in write mode before writing [OK]

Hint: Open file with 'w' or 'a' before writing CSV [OK]

Common Mistakes:

• Opening file in 'r' mode when writing
• Forgetting to close the file
• Misunderstanding fputcsv() input

5. You want to read a CSV file and write only rows where the third column is greater than 50 to a new CSV file. Which code snippet correctly implements this?

hard

A. $in = fopen('input.csv', 'w');
$out = fopen('output.csv', 'r');
while (($row = fgetcsv($in)) !== false) {
if ($row[2] > 50) {
fputcsv($out, $row);
}
}
fclose($in);
fclose($out);

B. $in = fopen('input.csv', 'r');
$out = fopen('output.csv', 'w');
while (($row = fgetcsv($in)) !== false) {
if ($row[2] > 50) {
fputcsv($out, $row);
}
}
fclose($in);
fclose($out);

C. $in = fopen('input.csv', 'r');
$out = fopen('output.csv', 'w');
while (($row = fgetcsv($out)) !== false) {
if ($row[2] > 50) {
fputcsv($in, $row);
}
}
fclose($in);
fclose($out);

D. $in = fopen('input.csv', 'r');
$out = fopen('output.csv', 'w');
while (($row = fgets($in)) !== false) {
if ($row[2] > 50) {
fputcsv($out, $row);
}
}
fclose($in);
fclose($out);

Solution

1. Step 1: Open input file for reading and output file for writing

   Use 'r' mode for reading input and 'w' mode for writing output.

2. Step 2: Read each CSV row with fgetcsv() from input and check third column

   Use fgetcsv($in) to read rows, then check if $row[2] > 50.

3. Step 3: Write qualifying rows to output with fputcsv()

   If condition passes, write row to output file using fputcsv($out, $row).

4. Final Answer:

   Code snippet B correctly reads, filters, and writes CSV rows -> Option B

5. Quick Check:

   Read with fgetcsv(), filter by column, write with fputcsv() [OK]

Hint: Read with fgetcsv(), filter rows, write with fputcsv() [OK]

Common Mistakes:

• Opening files with wrong modes
• Using fgets() instead of fgetcsv() for CSV reading
• Mixing input and output file handles