wp_unique_filename( string $dir, string $filename, callable $unique_filename_callback = null ): string

Description

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$dirstring

Directory.

$filenamestring

File name.

$unique_filename_callbackcallableoptional

Callback. Default null.Default: null

Return value

string

New filename, if given wasn't unique.

Performance profile

How much work a call to wp_unique_filename() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Heavy

Reads or writes the filesystem via file_exists().

Scaling

Scales with input

The body loops, so the work grows with what you pass in.

Instructions

71–181

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 323.

Plugin surface

2 hooks

Third-party callbacks on 'pre_wp_unique_filename_file_list', 'wp_unique_filename' run inside this call, and their cost is not bounded by anything here.

Called by

8

8 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• hookthird-party callbacksapply_filters()called directly
• filesystemfilesystem accessfile_exists()called directly

Further down the call graph this can also reach option, cache, serialize, query and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 200 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost wp_unique_filename() can have, taken from its control-flow graph on PHP 8.5.

This body has more branch combinations than are worth enumerating, so the table covers the outcomes found first rather than every one that exists.

Hooks and filters fired · 2

2 hooks fire while wp_unique_filename() runs, in this order:

1. 1
   apply_filters( pre_wp_unique_filename_file_list )filterline 2676 (+120 into the body)

   Filters the file list used for calculating a unique filename for a newly added file.

2. 2
   apply_filters( wp_unique_filename )filterline 2800 (+244 into the body)

   Filters the result when generating a unique file name.

Uses · 11

• sanitize_file_name()Sanitizes a filename, replacing whitespace with dashes.
• wp_check_filetype()Retrieves the file type from the file name.
• str_starts_with()Polyfill for `str_starts_with()` function added in PHP 8.0.
• wp_get_upload_dir()Retrieves uploads directory information.
• trailingslashit()Appends a trailing slash.
• str_contains()Polyfill for `str_contains()` function added in PHP 8.0.
• apply_filters()Calls the callback functions that have been added to a filter hook.
• _wp_check_existing_file_names()Helper function to check if a file name could match an existing image sub-size file name.
• wp_get_image_editor_output_format()Determines the output format for the image editor.
• wp_get_default_extension_for_mime_type()Returns the first matched extension for the mime type, as mapped from wp_get_mime_types().
• _wp_check_alternate_file_names()Helper function to test if each of an array of file names could conflict with existing files.

Used by · 8

• WP_REST_Attachments_Controller::edit_media_item()Applies edits to a media item and creates a new attachment record.
• _copy_image_file()Copies an existing image file.
• _wp_handle_upload()Handles PHP uploads in WordPress.
• wp_crop_image()Crops an image to a given size.
• wp_generate_attachment_metadata()Generates attachment meta data and create image sub-sizes for images.
• wp_privacy_generate_personal_data_export_file()Generate the personal data export file.
• wp_tempnam()Returns a filename of a temporary unique file.
• wp_upload_bits()Creates a file in the upload folder with given content.

Source code

View on Trac ↗View on GitHub ↗

2556function wp_unique_filename( $dir, $filename, $unique_filename_callback = null ) {2557	// Sanitize the file name before we begin processing.2558	$filename = sanitize_file_name( $filename );2559	$ext2     = null;2560 2561	// Initialize vars used in the wp_unique_filename filter.2562	$number        = '';2563	$alt_filenames = array();2564 2565	// Separate the filename into a name and extension.2566	$ext  = pathinfo( $filename, PATHINFO_EXTENSION );2567	$name = pathinfo( $filename, PATHINFO_BASENAME );2568 2569	if ( $ext ) {2570		$ext = '.' . $ext;2571	}2572 2573	// Edge case: if file is named '.ext', treat as an empty name.2574	if ( $name === $ext ) {2575		$name = '';2576	}2577 2578	/*2579	 * Increment the file number until we have a unique file to save in $dir.2580	 * Use callback if supplied.2581	 */2582	if ( $unique_filename_callback && is_callable( $unique_filename_callback ) ) {2583		$filename = call_user_func( $unique_filename_callback, $dir, $name, $ext );2584	} else {2585		$fname = pathinfo( $filename, PATHINFO_FILENAME );2586 2587		// Always append a number to file names that can potentially match image sub-size file names.2588		if ( $fname && preg_match( '/-(?:\d+x\d+|scaled|rotated)$/', $fname ) ) {2589			$number = 1;2590 2591			// At this point the file name may not be unique. This is tested below and the $number is incremented.2592			$filename = str_replace( "{$fname}{$ext}", "{$fname}-{$number}{$ext}", $filename );2593		}2594 2595		/*2596		 * Get the mime type. Uploaded files were already checked with wp_check_filetype_and_ext()2597		 * in _wp_handle_upload(). Using wp_check_filetype() would be sufficient here.2598		 */2599		$file_type = wp_check_filetype( $filename );2600		$mime_type = $file_type['type'];2601 2602		$is_image    = ( ! empty( $mime_type ) && str_starts_with( $mime_type, 'image/' ) );2603		$upload_dir  = wp_get_upload_dir();2604		$lc_filename = null;2605 2606		$lc_ext = strtolower( $ext );2607		$_dir   = trailingslashit( $dir );2608 2609		/*2610		 * If the extension is uppercase add an alternate file name with lowercase extension.2611		 * Both need to be tested for uniqueness as the extension will be changed to lowercase2612		 * for better compatibility with different filesystems. Fixes an inconsistency in WP < 2.92613		 * where uppercase extensions were allowed but image sub-sizes were created with2614		 * lowercase extensions.2615		 */2616		if ( $ext && $lc_ext !== $ext ) {2617			$lc_filename = preg_replace( '|' . preg_quote( $ext ) . '$|', $lc_ext, $filename );2618		}2619 2620		/*2621		 * Increment the number added to the file name if there are any files in $dir2622		 * whose names match one of the possible name variations.2623		 */2624		while ( file_exists( $_dir . $filename ) || ( $lc_filename && file_exists( $_dir . $lc_filename ) ) ) {2625			$new_number = (int) $number + 1;2626 2627			if ( $lc_filename ) {2628				$lc_filename = str_replace(2629					array( "-{$number}{$lc_ext}", "{$number}{$lc_ext}" ),2630					"-{$new_number}{$lc_ext}",2631					$lc_filename2632				);2633			}2634 2635			if ( '' === "{$number}{$ext}" ) {

Changelog

Introduced in 2.5.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

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Generated from the wordpress-develop 6.9.7 tag, from src/wp-includes/functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

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