File existence and info checks in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the file 'example.txt' exists.

PHP

<?php
if ([1]('example.txt')) {
    echo "File exists.";
} else {
    echo "File does not exist.";
}
?>

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

Afopen

Bis_file

Cfile_get_contents

Dfile_exists

Attempts:

3 left

💡 Hint

Common Mistakes

Using fopen without checking if the file exists causes errors.

Using is_file checks if it's a file but not if it exists in all cases.

The file_exists function checks if a file or directory exists at the given path.

2fill in blank

medium

Complete the code to check if 'data.csv' is a regular file.

PHP

<?php
if ([1]('data.csv')) {
    echo "It's a regular file.";
} else {
    echo "It's not a regular file.";
}
?>

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

Ais_file

Bis_dir

Cfile_exists

Dis_readable

Attempts:

3 left

💡 Hint

Common Mistakes

Using is_dir returns true only for directories.

Using file_exists returns true for files and directories.

The is_file function returns true if the path is a regular file.

3fill in blank

hard

Fix the error in the code to get the size of 'report.pdf'.

PHP

<?php
$size = [1]('report.pdf');
echo "File size: $size bytes.";
?>

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

Afilesizeof

Bfile_get_contents

Cfilesize

Dfile_exists

Attempts:

3 left

💡 Hint

Common Mistakes

Using file_get_contents returns the file content, not size.

Using filesizeof is not a valid PHP function.

The filesize function returns the size of the file in bytes.

4fill in blank

hard

Fill both blanks to check if 'image.png' is readable and writable.

PHP

<?php
if ([1]('image.png') && [2]('image.png')) {
    echo "File is readable and writable.";
} else {
    echo "File is not accessible for reading and writing.";
}
?>

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

Ais_readable

Bis_file

Cis_writable

Dfile_exists

Attempts:

3 left

💡 Hint

Common Mistakes

Using is_file only checks if it's a file, not permissions.

Using file_exists does not check permissions.

is_readable checks if the file can be read, and is_writable checks if it can be written.

5fill in blank

hard

Fill all three blanks to create an array with file names and their sizes for files larger than 1000 bytes in the 'docs' directory.

PHP

<?php
$files = scandir('docs');
$result = [];
foreach ($files as $file) {
    $path = 'docs/' . $[1];
    if (is_file($path) && filesize($path) [2] 1000) {
        $result[[3]] = filesize($path);
    }
}
print_r($result);
?>

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

Afile

B>

C$file

Dfilesize

Attempts:

3 left

💡 Hint

Common Mistakes

Using $files instead of $file in the path.

Using '<' instead of '>' for size comparison.

Using filesize($path) as the key instead of the file name.

We use file to build the path, check if the size is greater than 1000 bytes with >, and use $file as the key in the result array.

Practice

1. Which PHP function checks if a file or directory exists at a given path?

easy

A. filesize()

B. is_file()

C. file_exists()

D. is_readable()

Solution

1. Step 1: Understand the purpose of file_exists()

   The function file_exists() returns true if the file or directory exists at the specified path.

2. Step 2: Compare with other functions

   Functions like is_file() check if the path is a file, filesize() returns size, and is_readable() checks permissions, but none check existence alone.

3. Final Answer:

   file_exists() -> Option C

4. Quick Check:

   Check existence = file_exists() [OK]

Hint: Use file_exists() to check any file or directory presence [OK]

Common Mistakes:

• Confusing is_file() with existence check
• Using filesize() to check existence
• Assuming is_readable() means file exists

2. Which of the following is the correct syntax to check if a path is a directory in PHP?

easy

A. is_directory($path);

B. is_dir($path);

C. file_is_dir($path);

D. dir_exists($path);

Solution

1. Step 1: Recall the correct function name

   PHP uses is_dir() to check if a path is a directory.

2. Step 2: Verify syntax correctness

   The function is called as is_dir($path); other options are invalid function names.

3. Final Answer:

   is_dir($path); -> Option B

4. Quick Check:

   Directory check = is_dir() [OK]

Hint: Remember: is_dir() checks directories, not is_directory() [OK]

Common Mistakes:

• Using non-existent functions like is_directory()
• Mixing up is_file() and is_dir()
• Missing parentheses in function call

3. What will the following PHP code output if the file 'example.txt' exists and is 150 bytes in size?

$file = 'example.txt';
if (file_exists($file)) {
    echo filesize($file);
} else {
    echo 'File not found';
}

medium

A. 150

B. Error

C. 0

D. File not found

Solution

1. Step 1: Check file existence

   The code uses file_exists() to confirm 'example.txt' exists, which it does.

2. Step 2: Output file size

   Since the file exists, filesize($file) returns 150, which is printed.

3. Final Answer:

   150 -> Option A

4. Quick Check:

   File exists, output size = 150 [OK]

Hint: filesize() returns size only if file_exists() is true [OK]

Common Mistakes:

• Assuming filesize() works without checking existence
• Confusing filesize() output with file content
• Expecting 'File not found' when file exists

4. Identify the error in this PHP code snippet that checks if a file is writable:

$filename = 'data.txt';
if (is_writeable($filename)) {
    echo 'Writable';
} else {
    echo 'Not writable';
}

medium

A. Missing semicolon after echo statements

B. is_writeable() does not check permissions

C. $filename should be in double quotes

D. The function name is misspelled; should be is_writable()

Solution

1. Step 1: Check function spelling

   The correct function to check if a file is writable is is_writable(), not is_writeable().

2. Step 2: Verify other syntax

   Semicolons are present, variable quotes are valid, and is_writable() does check permissions.

3. Final Answer:

   The function name is misspelled; should be is_writable() -> Option D

4. Quick Check:

   Correct spelling = is_writable() [OK]

Hint: Remember: writable has one 'e' after writ [OK]

Common Mistakes:

• Misspelling is_writable() as is_writeable()
• Thinking variable needs double quotes
• Confusing permission check with existence

5. You want to list all files in a directory 'docs/' that exist, are readable, and have been modified in the last 24 hours. Which PHP code snippet correctly implements this?

hard

A. $files = scandir('docs/');
foreach ($files as $file) {
$path = 'docs/' . $file;
if (file_exists($path) && is_readable($path) && (time() - filemtime($path) < 86400)) {
echo $file . "\n";
}
}

B. $files = scandir('docs/');
foreach ($files as $file) {
if (is_dir($file)) continue;
if (is_writable($file)) {
echo $file . "\n";
}
}

C. $files = scandir('docs/');
foreach ($files as $file) {
if (file_exists($file) && filesize($file) > 0) {
echo $file . "\n";
}
}

D. $files = scandir('docs/');
foreach ($files as $file) {
if (is_file($file) && is_readable($file)) {
echo $file . "\n";
}
}

Solution

1. Step 1: Understand requirements

   We need to list files in 'docs/' that exist, are readable, and modified within last 24 hours (86400 seconds).

2. Step 2: Analyze each option

   $files = scandir('docs/'); foreach ($files as $file) { $path = 'docs/' . $file; if (file_exists($path) && is_readable($path) && (time() - filemtime($path) < 86400)) { echo $file . "\n"; } } correctly scans 'docs/', builds full path, checks file_exists(), is_readable(), and filemtime() against current time minus 86400 seconds. Other options miss one or more conditions or use wrong paths.

3. Final Answer:

   Option A code snippet -> Option A

4. Quick Check:

   Check existence + readability + recent mod = $files = scandir('docs/'); foreach ($files as $file) { $path = 'docs/' . $file; if (file_exists($path) && is_readable($path) && (time() - filemtime($path) < 86400)) { echo $file . "\n"; } } [OK]

Hint: Combine file_exists(), is_readable(), and filemtime() with full path [OK]

Common Mistakes:

• Not using full path when checking files
• Ignoring file modification time condition
• Checking is_writable() instead of is_readable()