_wp_utf8_decode_fallback( string $utf8_text ): string

Compatibility

Present in 3 of the 5 tracked releases, added in 6.9.0, and compiles on PHP 7.4 through 8.6-dev.

Parameters

$utf8_textstring

Text treated as UTF-8 bytes.

Return value

string

Text converted into ISO-8859-1.

Performance profile

How much work a call to _wp_utf8_decode_fallback() 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

Light

Touches nothing outside its own arguments.

Scaling

Scales with input

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

Instructions

13–38

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 77.

Plugin surface

None

Nothing here hands control to plugin code.

Called by

1

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

What one call costs · 2 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost _wp_utf8_decode_fallback() can have, taken from its control-flow graph on PHP 8.5.

Uses · 1

• _wp_scan_utf8()Finds spans of valid and invalid UTF-8 bytes in a given string.

Used by · 1

• utf8_decode()Converts a string from UTF-8 to ISO-8859-1.

Source code

View on Trac ↗View on GitHub ↗

487function _wp_utf8_decode_fallback( $utf8_text ) {488	$utf8_text       = (string) $utf8_text;489	$at              = 0;490	$was_at          = 0;491	$end             = strlen( $utf8_text );492	$iso_8859_1_text = '';493 494	while ( $at < $end ) {495		// US-ASCII bytes are identical in ISO-8859-1 and UTF-8. These are 0x00–0x7F.496		$ascii_byte_count = strspn(497			$utf8_text,498			"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f" .499			"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" .500			" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f",501			$at502		);503 504		if ( $ascii_byte_count > 0 ) {505			$at += $ascii_byte_count;506			continue;507		}508 509		$next_at        = $at;510		$invalid_length = 0;511		$found          = _wp_scan_utf8( $utf8_text, $next_at, $invalid_length, null, 1 );512		$span_length    = $next_at - $at;513		$next_byte      = '?';514 515		if ( 1 !== $found ) {516			if ( $invalid_length > 0 ) {517				$next_byte = '';518				goto flush_sub_part;519			}520 521			break;522		}523 524		// All convertible code points are two-bytes long.525		$byte1 = ord( $utf8_text[ $at ] );526		if ( 0xC0 !== ( $byte1 & 0xE0 ) ) {527			goto flush_sub_part;528		}529 530		// All convertible code points are not greater than U+FF.531		$byte2      = ord( $utf8_text[ $at + 1 ] );532		$code_point = ( ( $byte1 & 0x1F ) << 6 ) | ( ( $byte2 & 0x3F ) );533		if ( $code_point > 0xFF ) {534			goto flush_sub_part;535		}536 537		$next_byte = chr( $code_point );538 539		flush_sub_part:540		$iso_8859_1_text .= substr( $utf8_text, $was_at, $at - $was_at );541		$iso_8859_1_text .= $next_byte;542		$at              += $span_length;543		$was_at           = $at;544 545		if ( $invalid_length > 0 ) {546			$iso_8859_1_text .= '?';547			$at              += $invalid_length;548			$was_at           = $at;549		}550	}551 552	if ( 0 === $was_at ) {553		return $utf8_text;554	}555 556	$iso_8859_1_text .= substr( $utf8_text, $was_at );557	return $iso_8859_1_text;558}

Changelog

Introduced in 6.9.0. Unchanged from 6.9.7 through 7.1.0.

1. 6.9.7
2. 7.0.4
3. 7.1.0

Signature, return type and hooks compared across 3 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/compat-utf8.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

Corrections

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