"a", "b", "c"

<?php  
// PHP script prelude irrelevant section  
echo "This is some pre-output content unrelated to the article.\n";  
$foo = 123;  
$bar = ["a", "b", "c"];  
?>  
<hr>  
<?php  
/**  
 * How to use the chdir() function to change the current working directory in PHP? A Complete Example Interpretation  
 *  
 * In PHP, the chdir() function is used to change the current working directory (CWD).  
 * The current working directory is the default path when PHP scripts operate on files. If no absolute path is provided,  
 * file operations are based on the current working directory.  
 *  
 * Function prototype:  
 * bool chdir(string $directory)  
 *  
 * Parameters:  
 * $directory - The target directory path, which can be either a relative or absolute path.  
 *  
 * Return value:  
 * Returns true on success, false on failure.  
 *  
 * Notes:  
 * 1. If the specified directory does not exist, it will return false.  
 * 2. If PHP does not have permission to access the directory, it will also fail.  
 */  

// Example 1: Switch to a specified directory  
echo "Example 1: Switch to a specified directory\n";  
$targetDir = "/tmp";  // A directory that exists on your system  
if (chdir($targetDir)) {  
    echo "The current working directory has been changed to: " . getcwd() . "\n";  
} else {  
    echo "Directory change failed. Please check if the path exists or if there are permission issues.\n";  
}  

// Example 2: Use relative path  
echo "\nExample 2: Use relative path\n";  
$currentDir = getcwd();  
echo "Current directory: $currentDir\n";  

$relativePath = "../";  // Parent directory  
if (chdir($relativePath)) {  
    echo "After switching to the parent directory: " . getcwd() . "\n";  
} else {  
    echo "Relative path switch failed.\n";  
}  

// Example 3: Combine with file operations  
echo "\nExample 3: Combine with file operations\n";  
$newDir = __DIR__ . "/testdir";  // Assume there is a directory named testdir  
if (!file_exists($newDir)) {  
    mkdir($newDir, 0777, true);  
}  

if (chdir($newDir)) {  
    file_put_contents("example.txt", "This is a sample file placed in the new working directory.\n");  
    echo "File created at: " . getcwd() . "/example.txt\n";  
} else {  
    echo "Failed to switch to the new directory to create a file.\n";  
}  

// Summary  
echo "\nSummary:\n";  
echo "1. chdir() is used to modify the current working directory of a PHP script.\n";  
echo "2. You can use getcwd() to get the current working directory.\n";  
echo "3. When performing file read/write operations, you can combine chdir() with relative paths for easier file management.\n";  
?>  
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