82 	if ( null === $str ) {

    83 		return '';

    84 	}

    85 

   378 if ( ! function_exists( 'array_key_first' ) ) {

   379 	/**

   380 	 * Polyfill for array_key_first() function added in PHP 7.3.

   381 	 *

   382 	 * Get the first key of the given array without affecting

   383 	 * the internal array pointer.

   384 	 *

   385 	 * @since 5.9.0

   386 	 *

   387 	 * @param array $arr An array.

   388 	 * @return string|int|null The first key of array if the array

   389 	 *                         is not empty; `null` otherwise.

   390 	 */

   391 	function array_key_first( array $arr ) {

   392 		foreach ( $arr as $key => $value ) {

   393 			return $key;

   394 		}

   395 	}

   396 }

   397 

   398 if ( ! function_exists( 'array_key_last' ) ) {

   399 	/**

   400 	 * Polyfill for `array_key_last()` function added in PHP 7.3.

   401 	 *

   402 	 * Get the last key of the given array without affecting the

   403 	 * internal array pointer.

   404 	 *

   405 	 * @since 5.9.0

   406 	 *

   407 	 * @param array $arr An array.

   408 	 * @return string|int|null The last key of array if the array

   409 	 *.                        is not empty; `null` otherwise.

   410 	 */

   411 	function array_key_last( array $arr ) {

   412 		if ( empty( $arr ) ) {

   413 			return null;

   414 		}

   415 		end( $arr );

   416 		return key( $arr );

   417 	}

   418 }

   419 

   420 if ( ! function_exists( 'str_contains' ) ) {

   421 	/**

   422 	 * Polyfill for `str_contains()` function added in PHP 8.0.

   423 	 *

   424 	 * Performs a case-sensitive check indicating if needle is

   425 	 * contained in haystack.

   426 	 *

   427 	 * @since 5.9.0

   428 	 *

   429 	 * @param string $haystack The string to search in.

   430 	 * @param string $needle   The substring to search for in the haystack.

   431 	 * @return bool True if `$needle` is in `$haystack`, otherwise false.

   432 	 */

   433 	function str_contains( $haystack, $needle ) {

   434 		return ( '' === $needle || false !== strpos( $haystack, $needle ) );

   435 	}

   436 }

   437 

   438 if ( ! function_exists( 'str_starts_with' ) ) {

   439 	/**

   440 	 * Polyfill for `str_starts_with()` function added in PHP 8.0.

   441 	 *

   442 	 * Performs a case-sensitive check indicating if

   443 	 * the haystack begins with needle.

   444 	 *

   445 	 * @since 5.9.0

   446 	 *

   447 	 * @param string $haystack The string to search in.

   448 	 * @param string $needle   The substring to search for in the `$haystack`.

   449 	 * @return bool True if `$haystack` starts with `$needle`, otherwise false.

   450 	 */

   451 	function str_starts_with( $haystack, $needle ) {

   452 		if ( '' === $needle ) {

   453 			return true;

   454 		}

   455 		return 0 === strpos( $haystack, $needle );

   456 	}

   457 }

   458 

   459 if ( ! function_exists( 'str_ends_with' ) ) {

   460 	/**

   461 	 * Polyfill for `str_ends_with()` function added in PHP 8.0.

   462 	 *

   463 	 * Performs a case-sensitive check indicating if

   464 	 * the haystack ends with needle.

   465 	 *

   466 	 * @since 5.9.0

   467 	 *

   468 	 * @param string $haystack The string to search in.

   469 	 * @param string $needle   The substring to search for in the `$haystack`.

   470 	 * @return bool True if `$haystack` ends with `$needle`, otherwise false.

   471 	 */

   472 	function str_ends_with( $haystack, $needle ) {

   473 		if ( '' === $haystack && '' !== $needle ) {

   474 			return false;

   475 		}

   476 		$len = strlen( $needle );

   477 		return 0 === substr_compare( $haystack, $needle, -$len, $len );

   478 	}

   479 }

   480