public static function valid($str)
	{
		// Cached expected number of octets after the current octet
		// until the beginning of the next UTF8 character sequence
		$mState = 0;

		// Cached Unicode character
		$mUcs4 = 0;

		// Cached expected number of octets in the current sequence
		$mBytes = 1;

		$len = strlen($str);

		for ($i = 0; $i < $len; $i++)
		{
			$in = ord($str{$i});

			if ($mState == 0)
			{
				// When mState is zero we expect either a US-ASCII character or a
				// multi-octet sequence.
				if (0 == (0x80 & ($in)))
				{
					// US-ASCII, pass straight through.
					$mBytes = 1;
				}
				elseif (0xC0 == (0xE0 & ($in)))
				{
					// First octet of 2 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x1F) << 6;
					$mState = 1;
					$mBytes = 2;
				}
				elseif (0xE0 == (0xF0 & ($in)))
				{
					// First octet of 3 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x0F) << 12;
					$mState = 2;
					$mBytes = 3;
				}
				elseif (0xF0 == (0xF8 & ($in)))
				{
					// First octet of 4 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x07) << 18;
					$mState = 3;
					$mBytes = 4;
				}
				elseif (0xF8 == (0xFC & ($in)))
				{
					// First octet of 5 octet sequence.
					//
					// This is illegal because the encoded codepoint must be either
					// (a) not the shortest form or
					// (b) outside the Unicode range of 0-0x10FFFF.
					// Rather than trying to resynchronize, we will carry on until the end
					// of the sequence and let the later error handling code catch it.
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x03) << 24;
					$mState = 4;
					$mBytes = 5;
				}
				elseif (0xFC == (0xFE & ($in)))
				{
					// First octet of 6 octet sequence, see comments for 5 octet sequence.
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 1) << 30;
					$mState = 5;
					$mBytes = 6;
				}
				else
				{
					// Current octet is neither in the US-ASCII range nor a legal first
					// octet of a multi-octet sequence.
					return false;
				}
			}
			else
			{
				// When mState is non-zero, we expect a continuation of the multi-octet
				// sequence
				if (0x80 == (0xC0 & ($in)))
				{
					// Legal continuation.
					$shift = ($mState - 1) * 6;
					$tmp = $in;
					$tmp = ($tmp & 0x0000003F) << $shift;
					$mUcs4 |= $tmp;

					// End of the multi-octet sequence. mUcs4 now contains the final
					// Unicode codepoint to be output
					if (0 == --$mState)
					{
						// Check for illegal sequences and codepoints.
						// From Unicode 3.1, non-shortest form is illegal
						if (((2 == $mBytes) && ($mUcs4 < 0x0080)) || ((3 == $mBytes) && ($mUcs4 < 0x0800)) || ((4 == $mBytes) && ($mUcs4 < 0x10000))
							|| (4 < $mBytes)
							|| (($mUcs4 & 0xFFFFF800) == 0xD800) // From Unicode 3.2, surrogate characters are illegal
							|| ($mUcs4 > 0x10FFFF)) // Codepoints outside the Unicode range are illegal
						{
							return false;
						}

						// Initialize UTF8 cache.
						$mState = 0;
						$mUcs4 = 0;
						$mBytes = 1;
					}
				}
				else
				{
					//((0xC0 & (*in) != 0x80) && (mState != 0))
					// Incomplete multi-octet sequence.
					return false;
				}
			}
		}

		return true;
	}
public static function valid($str)
	{
		// Cached expected number of octets after the current octet
		// until the beginning of the next UTF8 character sequence
		$mState = 0;

		// Cached Unicode character
		$mUcs4 = 0;

		// Cached expected number of octets in the current sequence
		$mBytes = 1;

		$len = strlen($str);

		for ($i = 0; $i < $len; $i++)
		{
			$in = ord($str{$i});

			if ($mState == 0)
			{
				// When mState is zero we expect either a US-ASCII character or a
				// multi-octet sequence.
				if (0 == (0x80 & ($in)))
				{
					// US-ASCII, pass straight through.
					$mBytes = 1;
				}
				elseif (0xC0 == (0xE0 & ($in)))
				{
					// First octet of 2 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x1F) << 6;
					$mState = 1;
					$mBytes = 2;
				}
				elseif (0xE0 == (0xF0 & ($in)))
				{
					// First octet of 3 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x0F) << 12;
					$mState = 2;
					$mBytes = 3;
				}
				elseif (0xF0 == (0xF8 & ($in)))
				{
					// First octet of 4 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x07) << 18;
					$mState = 3;
					$mBytes = 4;
				}
				elseif (0xF8 == (0xFC & ($in)))
				{
					// First octet of 5 octet sequence.
					//
					// This is illegal because the encoded codepoint must be either
					// (a) not the shortest form or
					// (b) outside the Unicode range of 0-0x10FFFF.
					// Rather than trying to resynchronize, we will carry on until the end
					// of the sequence and let the later error handling code catch it.
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x03) << 24;
					$mState = 4;
					$mBytes = 5;
				}
				elseif (0xFC == (0xFE & ($in)))
				{
					// First octet of 6 octet sequence, see comments for 5 octet sequence.
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 1) << 30;
					$mState = 5;
					$mBytes = 6;
				}
				else
				{
					// Current octet is neither in the US-ASCII range nor a legal first
					// octet of a multi-octet sequence.
					return false;
				}
			}
			else
			{
				// When mState is non-zero, we expect a continuation of the multi-octet
				// sequence
				if (0x80 == (0xC0 & ($in)))
				{
					// Legal continuation.
					$shift = ($mState - 1) * 6;
					$tmp = $in;
					$tmp = ($tmp & 0x0000003F) << $shift;
					$mUcs4 |= $tmp;

					// End of the multi-octet sequence. mUcs4 now contains the final
					// Unicode codepoint to be output
					if (0 == --$mState)
					{
						// Check for illegal sequences and codepoints.
						// From Unicode 3.1, non-shortest form is illegal
						if (((2 == $mBytes) && ($mUcs4 < 0x0080)) || ((3 == $mBytes) && ($mUcs4 < 0x0800)) || ((4 == $mBytes) && ($mUcs4 < 0x10000))
							|| (4 < $mBytes)
							|| (($mUcs4 & 0xFFFFF800) == 0xD800) // From Unicode 3.2, surrogate characters are illegal
							|| ($mUcs4 > 0x10FFFF)) // Codepoints outside the Unicode range are illegal
						{
							return false;
						}

						// Initialize UTF8 cache.
						$mState = 0;
						$mUcs4 = 0;
						$mBytes = 1;
					}
				}
				else
				{
					//((0xC0 & (*in) != 0x80) && (mState != 0))
					// Incomplete multi-octet sequence.
					return false;
				}
			}
		}

		return true;
	}
public static function valid ( $ str ) { // Cached expected number of octets after the current octet // until the beginning of the next UTF8 character sequence $ mState = 0 ; // Cached Unicode character $ mUcs4 = 0 ; // Cached expected number of octets in the current sequence $ mBytes = 1 ; $ len = strlen ( $ str ) ; for ( $ i = 0 ; $ i < $ len ; $ i ++ ) { $ in = ord ( $ str { $ i } ) ; if ( $ mState == 0 ) { // When mState is zero we expect either a US-ASCII character or a // multi-octet sequence. if ( 0 == ( 0x80 & ( $ in ) ) ) { // US-ASCII, pass straight through. $ mBytes = 1 ; } elseif ( 0xC0 == ( 0xE0 & ( $ in ) ) ) { // First octet of 2 octet sequence $ mUcs4 = ( $ in ) ; $ mUcs4 = ( $ mUcs4 & 0x1F ) << 6 ; $ mState = 1 ; $ mBytes = 2 ; } elseif ( 0xE0 == ( 0xF0 & ( $ in ) ) ) { // First octet of 3 octet sequence $ mUcs4 = ( $ in ) ; $ mUcs4 = ( $ mUcs4 & 0x0F ) << 12 ; $ mState = 2 ; $ mBytes = 3 ; } elseif ( 0xF0 == ( 0xF8 & ( $ in ) ) ) { // First octet of 4 octet sequence $ mUcs4 = ( $ in ) ; $ mUcs4 = ( $ mUcs4 & 0x07 ) << 18 ; $ mState = 3 ; $ mBytes = 4 ; } elseif ( 0xF8 == ( 0xFC & ( $ in ) ) ) { // First octet of 5 octet sequence. // // This is illegal because the encoded codepoint must be either // (a) not the shortest form or // (b) outside the Unicode range of 0-0x10FFFF. // Rather than trying to resynchronize, we will carry on until the end // of the sequence and let the later error handling code catch it. $ mUcs4 = ( $ in ) ; $ mUcs4 = ( $ mUcs4 & 0x03 ) << 24 ; $ mState = 4 ; $ mBytes = 5 ; } elseif ( 0xFC == ( 0xFE & ( $ in ) ) ) { // First octet of 6 octet sequence, see comments for 5 octet sequence. $ mUcs4 = ( $ in ) ; $ mUcs4 = ( $ mUcs4 & 1 ) << 30 ; $ mState = 5 ; $ mBytes = 6 ; } else { // Current octet is neither in the US-ASCII range nor a legal first // octet of a multi-octet sequence. return false ; } } else { // When mState is non-zero, we expect a continuation of the multi-octet // sequence if ( 0x80 == ( 0xC0 & ( $ in ) ) ) { // Legal continuation. $ shift = ( $ mState - 1 ) * 6 ; $ tmp = $ in ; $ tmp = ( $ tmp & 0x0000003F ) << $ shift ; $ mUcs4 |= $ tmp ; // End of the multi-octet sequence. mUcs4 now contains the final // Unicode codepoint to be output if ( 0 == -- $ mState ) { // Check for illegal sequences and codepoints. // From Unicode 3.1, non-shortest form is illegal if ( ( ( 2 == $ mBytes ) && ( $ mUcs4 < 0x0080 ) ) || ( ( 3 == $ mBytes ) && ( $ mUcs4 < 0x0800 ) ) || ( ( 4 == $ mBytes ) && ( $ mUcs4 < 0x10000 ) ) || ( 4 < $ mBytes ) || ( ( $ mUcs4 & 0xFFFFF800 ) == 0xD800 ) // From Unicode 3.2, surrogate characters are illegal || ( $ mUcs4 > 0x10FFFF ) ) // Codepoints outside the Unicode range are illegal { return false ; } // Initialize UTF8 cache. $ mState = 0 ; $ mUcs4 = 0 ; $ mBytes = 1 ; } } else { //((0xC0 & (*in) != 0x80) && (mState != 0)) // Incomplete multi-octet sequence. return false ; } } } return true ; }
Tests a string as to whether it's valid UTF-8 and supported by the Unicode standard.

Note: this function has been modified to simple return true or false.

@param   string   $str  UTF-8 encoded string.
@return  boolean  true if valid
Tests a string as to whether it s valid UTF - 8 and supported by the Unicode standard .